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Beyond Weird: Why Everything You Thought You Knew about Quantum Physics Is Different
“Anyone who is not shocked by quantum theory has not understood it.�
Since Niels Bohr said this many years ago, quantum mechanics has only been getting more shocking. We now realize that it’s not really telling us that “weird� things happen out of sight, on the tiniest level, in the atomic world: rather, everything is quantum. But if quantum mechanics is correct, what seems obvious and right in our everyday world is built on foundations that don’t seemobvious or right at all—or even possible.
An exhilarating tour of the contemporary quantum landscape,Beyond Weirdis a book about what quantum physics really means—and what it doesn’t. Science writer Philip Ball offers an up-to-date, accessible account of the quest to come to grips with the most fundamental theory of physical reality, and to explain how its counterintuitive principles underpin the world we experience. Over the past decade it has become clear that quantum physics is less a theory about particles and waves, uncertainty and fuzziness, than a theory about information and knowledge—about what can be known, and how we can know it. Discoveries and experiments over the past few decades have called into question the meanings and limits of space and time, cause and effect, and, ultimately, of knowledge itself. The quantum world Ball shows us isn’t a different world. It is our world, and if anything deserves to be called “weird,� it’s us.
Since Niels Bohr said this many years ago, quantum mechanics has only been getting more shocking. We now realize that it’s not really telling us that “weird� things happen out of sight, on the tiniest level, in the atomic world: rather, everything is quantum. But if quantum mechanics is correct, what seems obvious and right in our everyday world is built on foundations that don’t seemobvious or right at all—or even possible.
An exhilarating tour of the contemporary quantum landscape,Beyond Weirdis a book about what quantum physics really means—and what it doesn’t. Science writer Philip Ball offers an up-to-date, accessible account of the quest to come to grips with the most fundamental theory of physical reality, and to explain how its counterintuitive principles underpin the world we experience. Over the past decade it has become clear that quantum physics is less a theory about particles and waves, uncertainty and fuzziness, than a theory about information and knowledge—about what can be known, and how we can know it. Discoveries and experiments over the past few decades have called into question the meanings and limits of space and time, cause and effect, and, ultimately, of knowledge itself. The quantum world Ball shows us isn’t a different world. It is our world, and if anything deserves to be called “weird,� it’s us.
370 pages, Kindle Edition
First published March 22, 2018
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About the author
Philip Ball
69books464followersPhilip Ball (born 1962) is an English science writer. He holds a degree in chemistry from Oxford and a doctorate in physics from Bristol University. He was an editor for the journal Nature for over 10 years. He now writes a regular column in Chemistry World. Ball's most-popular book is the 2004 Critical Mass: How One Things Leads to Another, winner of the 2005 Aventis Prize for Science Books. It examines a wide range of topics including the business cycle, random walks, phase transitions, bifurcation theory, traffic flow, Zipf's law, Small world phenomenon, catastrophe theory, the Prisoner's dilemma. The overall theme is one of applying modern mathematical models to social and economic phenomena.
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July 23, 2019
The Fault, Dear Brutus, Is Not in Our Stars
Quantum theory is probably the best possible proof of the validity of Pragmatist philosophy. No one understands what the theory means. And as Philip Ball says, “No one tells you that it often lacks any justification beyond the mere (and obviously important) fact that it works.� And this has a startling implication: It’s not just the physical world that is different from what we thought; reason itself must be something much more obscure than we have ever conceived. Both the scientific route to quantum theory and the meaning of that theory contradict our most dearly held principles of correct thinking, or for that matter our most deeply engrained image of ourselves.
Ball takes an intriguing perspective. Most commentators on quantum physics, possibly most scientists, consider its contradictions - entanglement, wave/particle ambiguity, simultaneous existence and non-existence, etc. - as indications that the theory is incomplete, that some further theoretical breakthrough will resolve these contradictions and make it more rational. Ball doesn’t do that. Suppose, he suggests, “the apparent oddness, the paradoxes and puzzles of quantum mechanics, are real.� What we are then confronted with is a challenge to think differently because the world demands that we do so.
If reality is as quantum physics says it is, we don’t need a better physics, we need to reconsider what we mean when we use words like ‘reasonable�, and ‘rational�, and ‘logical�, and even ‘knowing�. If reality is as quantum physics says it is, we need to re-learn what it means to learn - not just about physics but about everything. If reality is as quantum physics says it is, the real issue isn’t about matter and energy but about mind. We may know far less than we thought we knew about what constitutes this dominant human capacity for making sense of the world because what it means to make sense doesn’t anymore. Quantum physics “calls into question the meanings and limits of space and time, cause and effect, and knowledge itself.�
Ball’s thesis is that quantum theory isn’t even about physics, it’s about information: “We now realise that quantum mechanics is less about particles and waves, uncertainty and fuzziness, than a theory about information: about what can be known and how.� In other words quantum theory is the key to an entirely new epistemology, an unexpected kind of ‘knowability�. As a species, we have stumbled across something more fundamental than another tool for exploiting the universe. We may, instead, have an impetus (or at least invitation) for beginning to investigate and understand ourselves in a new way.
This is clearly exciting stuff. When Ball points out that quantum theory “is not so much a theory that one can test by observation and measurement, but a theory about what it means to observe and measure,� he is implying that it is a theory of being human, a cosmic anthropology perhaps. After all, isn’t that what we spend most of our lives as human beings doing? Observing, comparatively assessing, and judging everything? If quantum theory is a theory of those things, it is a theory of us. It is certainly not a fully worked out theory but it does give a clear direction which is rather different than any other ever proposed.
For example, a central issue of quantum theory is measurement. Essentially, measurement is not a neutral act; it changes the character of the thing measured in some annoying ways. There is no such thing as ‘unobtrusive measurement� in quantum physics. This challenges the idea of measurement as something which observes and comparatively assesses the properties of an object. The results of experimentation show that this is not the case. Measurement is not the assessment of the inherent properties of an object, it is the assignment of an object as a property of a scale of measurement, a metric.* This is the case as much in the ‘macro� world we inhabit as it is in that of atomic particles. We just haven’t needed to recognise the fact.
So, this is a revelation of quantum physics: there are no inherent properties. ‘Properties� are not inherent in anything. They are essentially scales on which we assign a place to events, objects, or relationships. As it turns out, sometimes the scales are incompatible with each other. Nothing to do with the object; everything to do with the scales. There is absolutely nothing ‘objective� about these scales; they are chosen for some reason, some human reason, that has nothing to do with the phenomenon in question. These scales are not merely the basis for further judgment, they are themselves a judgment about what’s important in the world. That is, they are always subjective in the sense that they have a personal import to the one who chooses them.
The ‘meaning� of quantum uncertainty, therefore, is fundamentally aesthetical and ethical, even in scientific research. The choice of a metric always means the rejection of other metrics. And the positive choice is not nearly so significant as the exclusion of the myriad of other possible metrics which could have been used to assess a phenomenon. The choice even at the quantum level is not binary - position vs. momentum - it is so for any number of so-called conjugate variables; and any choice means that an infinite number of other things will not be ‘observed,� that is assigned a place on alternative metrics. This is one interpretation of the process of ‘replication� of quantum events. The ‘imprint� of the event is what is left on the metric; and if it is left 0n one it cannot be left on another. The event is quite literally a property of the metric which ‘absorbs� information making it unavailable as a property of another metric.
These musings on measurement are mine not Ball’s; but I think they conform with the spirit of his analysis of quantum theory: “Rather than insisting on its difficulty, we might better regard it as a beguiling, maddening, even amusing gauntlet thrown down to challenge the imagination. For that is indeed what is challenged.� I imagine a logic which has yet to be articulated, specifically a logic of permissible choices of criteria of judgment. Such a logic would be both aesthetic and moral. It would also explicitly acknowledge that it is inevitable that we project our aesthetic and moral selves upon the world (as we do with the idea of a wave function - actually instructions for how to measure - which then allows the calculation of all sorts of ‘properties� which are derived from these instructions). Perhaps most important is the recognition in this logic that we have a choice, and therefore a responsibility, about what we project. If we don’t know why we make certain choices, then we have a duty to find out.
The applicability of such a logic is of course not confined to measurement. Measurement is one activity in the more general realm of language (which in turn is a component of information, that are all elements, perhaps the only elements, of mind). This suggests that there might be an aesthetic/moral logic of language that overrides categories like vocabulary, grammar, and pragmatics. Perhaps that is what literature is meant to do - uncover the hidden quantum logic of language one story at a time. And that logic exists, if it does at all, in mind not matter. Or if that way of expressing it is prejudicial, perhaps it would be better to say that it exists in matter as incipient mind. Matter merely awaits its turn at mind... and vice-versa. Meanwhile mind tells stories about matter, and there is nothing to compare these stories with... except other stories. Matter, of course, remains mute on the subject and just lurks, biding its time.
*See for further discussion: /review/show...
Quantum theory is probably the best possible proof of the validity of Pragmatist philosophy. No one understands what the theory means. And as Philip Ball says, “No one tells you that it often lacks any justification beyond the mere (and obviously important) fact that it works.� And this has a startling implication: It’s not just the physical world that is different from what we thought; reason itself must be something much more obscure than we have ever conceived. Both the scientific route to quantum theory and the meaning of that theory contradict our most dearly held principles of correct thinking, or for that matter our most deeply engrained image of ourselves.
Ball takes an intriguing perspective. Most commentators on quantum physics, possibly most scientists, consider its contradictions - entanglement, wave/particle ambiguity, simultaneous existence and non-existence, etc. - as indications that the theory is incomplete, that some further theoretical breakthrough will resolve these contradictions and make it more rational. Ball doesn’t do that. Suppose, he suggests, “the apparent oddness, the paradoxes and puzzles of quantum mechanics, are real.� What we are then confronted with is a challenge to think differently because the world demands that we do so.
If reality is as quantum physics says it is, we don’t need a better physics, we need to reconsider what we mean when we use words like ‘reasonable�, and ‘rational�, and ‘logical�, and even ‘knowing�. If reality is as quantum physics says it is, we need to re-learn what it means to learn - not just about physics but about everything. If reality is as quantum physics says it is, the real issue isn’t about matter and energy but about mind. We may know far less than we thought we knew about what constitutes this dominant human capacity for making sense of the world because what it means to make sense doesn’t anymore. Quantum physics “calls into question the meanings and limits of space and time, cause and effect, and knowledge itself.�
Ball’s thesis is that quantum theory isn’t even about physics, it’s about information: “We now realise that quantum mechanics is less about particles and waves, uncertainty and fuzziness, than a theory about information: about what can be known and how.� In other words quantum theory is the key to an entirely new epistemology, an unexpected kind of ‘knowability�. As a species, we have stumbled across something more fundamental than another tool for exploiting the universe. We may, instead, have an impetus (or at least invitation) for beginning to investigate and understand ourselves in a new way.
This is clearly exciting stuff. When Ball points out that quantum theory “is not so much a theory that one can test by observation and measurement, but a theory about what it means to observe and measure,� he is implying that it is a theory of being human, a cosmic anthropology perhaps. After all, isn’t that what we spend most of our lives as human beings doing? Observing, comparatively assessing, and judging everything? If quantum theory is a theory of those things, it is a theory of us. It is certainly not a fully worked out theory but it does give a clear direction which is rather different than any other ever proposed.
For example, a central issue of quantum theory is measurement. Essentially, measurement is not a neutral act; it changes the character of the thing measured in some annoying ways. There is no such thing as ‘unobtrusive measurement� in quantum physics. This challenges the idea of measurement as something which observes and comparatively assesses the properties of an object. The results of experimentation show that this is not the case. Measurement is not the assessment of the inherent properties of an object, it is the assignment of an object as a property of a scale of measurement, a metric.* This is the case as much in the ‘macro� world we inhabit as it is in that of atomic particles. We just haven’t needed to recognise the fact.
So, this is a revelation of quantum physics: there are no inherent properties. ‘Properties� are not inherent in anything. They are essentially scales on which we assign a place to events, objects, or relationships. As it turns out, sometimes the scales are incompatible with each other. Nothing to do with the object; everything to do with the scales. There is absolutely nothing ‘objective� about these scales; they are chosen for some reason, some human reason, that has nothing to do with the phenomenon in question. These scales are not merely the basis for further judgment, they are themselves a judgment about what’s important in the world. That is, they are always subjective in the sense that they have a personal import to the one who chooses them.
The ‘meaning� of quantum uncertainty, therefore, is fundamentally aesthetical and ethical, even in scientific research. The choice of a metric always means the rejection of other metrics. And the positive choice is not nearly so significant as the exclusion of the myriad of other possible metrics which could have been used to assess a phenomenon. The choice even at the quantum level is not binary - position vs. momentum - it is so for any number of so-called conjugate variables; and any choice means that an infinite number of other things will not be ‘observed,� that is assigned a place on alternative metrics. This is one interpretation of the process of ‘replication� of quantum events. The ‘imprint� of the event is what is left on the metric; and if it is left 0n one it cannot be left on another. The event is quite literally a property of the metric which ‘absorbs� information making it unavailable as a property of another metric.
These musings on measurement are mine not Ball’s; but I think they conform with the spirit of his analysis of quantum theory: “Rather than insisting on its difficulty, we might better regard it as a beguiling, maddening, even amusing gauntlet thrown down to challenge the imagination. For that is indeed what is challenged.� I imagine a logic which has yet to be articulated, specifically a logic of permissible choices of criteria of judgment. Such a logic would be both aesthetic and moral. It would also explicitly acknowledge that it is inevitable that we project our aesthetic and moral selves upon the world (as we do with the idea of a wave function - actually instructions for how to measure - which then allows the calculation of all sorts of ‘properties� which are derived from these instructions). Perhaps most important is the recognition in this logic that we have a choice, and therefore a responsibility, about what we project. If we don’t know why we make certain choices, then we have a duty to find out.
The applicability of such a logic is of course not confined to measurement. Measurement is one activity in the more general realm of language (which in turn is a component of information, that are all elements, perhaps the only elements, of mind). This suggests that there might be an aesthetic/moral logic of language that overrides categories like vocabulary, grammar, and pragmatics. Perhaps that is what literature is meant to do - uncover the hidden quantum logic of language one story at a time. And that logic exists, if it does at all, in mind not matter. Or if that way of expressing it is prejudicial, perhaps it would be better to say that it exists in matter as incipient mind. Matter merely awaits its turn at mind... and vice-versa. Meanwhile mind tells stories about matter, and there is nothing to compare these stories with... except other stories. Matter, of course, remains mute on the subject and just lurks, biding its time.
*See for further discussion: /review/show...
November 15, 2020
Ask scientists what quantum mechanics tells us and you will get a variety of contradictory explanations. Where does that leave the rest of us? Ball tries to help us understand the issues around quantum mechanics. He provides perspectives I had not read before. He employs science as well as philosophy. For language, while inadequate on many occasions, is at a total loss when it comes to the quantum. In Ball’s words “In quantum theory, words are blunt tools. We give names to things and processes, but those are just labels for concepts that cannot be properly, accurately expressed in any terms but their own.� If words won’t do, what about the math? Scientists may say “the math makes perfect sense whereas the words don’t quite. But that would be to make a semantic error: equations about physical reality are, without interpretation, just marks on paper. We can’t hide behind equations from that ‘not quite� � not if we truly want to derive meaning.�
Take the issue of wave-particle duality. Ball notes “Quantum objects are not sometimes particles and sometimes waves…we have no reason to suppose that ‘what they are� changes in any meaningful way depending on how we try to look at them. So the phrase ‘wave-particle duality� doesn’t really refer to quantum objects at all, but the interpretation of experiments…� “Einstein expressed it by saying that quantum objects present us with a choice of languages, but it is too easily forgotten that this is precisely what it is: a struggle to formulate the right words, not a description of the reality behind them.�
Erwin Schrodinger developed a wave equation for an electron substituting electrical charge for amplitude, which normal wave equations represent. Ball goes on “It was a natural thing to assume, but it was wrong. The wave in Schrodinger’s wave isn’t a wave of electron charge density. In fact, it’s not a wave that corresponds to any concrete physical property. It is just a mathematical abstraction � for which reason it is not really a wave at all, but is called a wavefunction.� The wavefunction, however, is useful. It can determine probabilities such as finding a quantum object in a particular position or with a particular momentum or energy, depending on the experiment. Ball continues “And - here’s the really important thing � this wavefunction contains all the information one can possibly access about the corresponding quantum particle.� But even though you can get a probability of finding an electron in a particular place, the wavefunction �says nothing about where the electron is.� “The wavefunction is not a description of the entity we call an electron. It is a prescription for what to expect when we make measurements on that entity�. Many physicists would disagree with that statement, but it represents the thinking of Niels Bohr and those that subscribe to the Copenhagen Interpretation.
While Ball accepts that quantum mechanics does not describe an underlying reality, he doesn’t believe that means there isn’t one. However, Ball is not a realist. Most scientists who are realists know that the wavefunction is not a real description of the underlying reality, but believe that it corresponds to an objective reality. After all, what produces the measurements we make? This realist view is the ontic view as opposed to the epistemic view of the Copenhagenists. In the latter view we only get probabilities for the result of our measurements, but can’t even speak of an underlying reality.
The idea of superposition, that a quantum object can be in two or more places or two or more states at the same time runs into arguments similar to those for wave-particle duality. The wavefunction is a solution to Schrodinger’s equation, which like other equations can have multiple solutions which can be combined. These multiple solutions can be considered separate states but it is a matter of interpretation. Ball notes “But strictly speaking a superposition should be considered only as an abstract mathematical thing.� In a normal wave equation another solution is just another wave, but because Schrodinger is using wave physics for quantum states it gets confusing. In Ball’s words “superpositions of quantum states only seem odd because the wavefunctions are used to describe the properties of entities that we can also regard as particles � meaning that such particles seem to be able to have two or more values of their properties at once.�
The double-slit experiment not only seems to show that an electron can take two paths at once like a wave, but that it can switch back to particle behavior taking only one path when observed. There is no explanation for this, but there is no reason to assume that the quantum object actually changes. For more on the double slit experiment I highly recommend reading Anil Ananthaswamy’s Through Two Doors at Once. With descriptions of many types of double slit experiments, he really gets you to appreciate just how strange quantum mechanics is. He shows that not only does a particle appear to take two paths at the same time but seems to go back in time which Ball also alludes to. Feynman’s quantum electrodynamics is sometimes used to support a particle taking multiple paths, but does the mathematics actually represent reality. In the calculations, most paths cancel out. Ball says it is a flat out wrong assumption, �The electron or photon does not take all possible paths.�
Ball thinks Heisenberg’s Uncertainty Principle would be better called the Unknowable Principle. We can’t measure multiple quantum properties at the same time �because they can’t exist all at once. And by gathering some we may scramble the values of others.� The order in which measurements are made makes a difference. Ball points out that measurements of spin components change based on the order. Measuring one scrambles the measurement of the other. Ball gives a very good explanation of “spin�, electron orbits, and quantum numbers that are used to define quantum states. Some variables can be measured accurately at the same time such as mass and charge but others known as conjugate variables have limited accuracy when measured at the same time - the more precise the measurement of one, the less precise the measurement of the other. Position and momentum are conjugate variables as are energy and time. Why these and not others? Ball cannot think of an intuitive explanation, but he says it’s in the math. Heisenberg’s matrix mechanics solution is not commutative for these properties. A times B does not equal B times A. The difference between the calculations is the difference in accuracy of the Uncertainty Principle. Regarding momentum and measurement, momentum in waves is measured by wave length, something not conducive to a precise position measurement. Ball explains this in more detail. Sean Carroll in Something Deeply Hidden also does a very good job of explaining this.
Then there is the issue of entanglement. Ball describes this as quantum objects with shared properties represented by a single wavefunction, even though they may be far distant from each other in space. “As far as quantum mechanics is concerned, entanglement makes them both parts of a single object.� In experiments the spin of entangled electrons isn’t correlated because they communicate with each other, but because the property of spin is non-local in entangled electrons. Ball notes “The main thing you need to know about entanglement is this: it tells us that a quantum object may have properties that are not entirely located on that object.� Some physicists suspect that entanglement is what ties together spacetime. In one model “spacetime and gravity in the 3D universe look like a projection of the entanglement existing within its 2D boundary surface.� Entanglement may also be important to developing a theory of quantum gravity. Carlo Rovelli’s Reality is Not What it Seems gives an accessible description of loop quantum gravity and how spacetime could emerge from the quantum. Rovelli embraces Heisenberg’s matrix solution to quantum mechanics, but sees Schrodinger’s wave function only as an aid to calculation.
Next Ball discusses where the quantum world ends and the classical world begins. It’s not a matter of size. Rather it is a loss of coherence or decoherence. The Schrodinger equation describes quantum objects in terms of abstract waves that determine probabilities. Ball notes “It is this waviness that gives rise to distinctly quantum phenomena like, interference, superposition and entanglement. These behaviours become possible when there is a well-defined relationship between the quantum ‘waves�: in effect when they are in step. This coordination is called coherence.� Without coherence “there can be no regular interference pattern, but just random, featureless variations in the resulting wave amplitude.� When a quantum object encounters another object it becomes entangled with it. Given the abundance of photons, air molecules, dust grains and such in the environment, this entanglement rapidly spreads. The quantum object’s individual superposition is lost when it becomes a part of the wavefunction of the larger object. These classical objects are decoherent and do not display quantum superposition or interference. The classical world grows out of the quantum world. It is not separate from it.
Ball devotes a couple of chapters to quantum computing. The increased speed of quantum computers is commonly ascribed to superposition, accessing more than one state of each qubit. For this the qubits must maintain coherence and not get entangled with their environment. This is a technological challenge, and so far quantum computers have only been able to maintain a small number of qubits in their quantum state for long enough to perform calculations. So it may be a while before quantum computers challenge conventional ones. Ball sees quantum computers as having excellent potential for specific tasks such as factoring large numbers, important to cryptography, and also for large data base searches. He doubts that they will replace your laptop for everyday tasks. He also points out that there are skeptics of the idea that quantum computers achieve their speed through parallel processing due to superposition of the qubits. Rather the increased performance may be due to qubits entangled with each other allowing them to be managed together rather than in separate steps saving time. There are other theories, but no consensus. Ball states point blank that “no one fully understands how quantum computers work.�
Ball analyzes some of the interpretations. Copenhagen is his starting point. He shows great respect for Bohr and much of what he said, but takes exception to the notion that there will never be a way to find out more about the quantum world. From there he looks at the de Broglie-Bohm interpretation, the GRW collapse model, the Penrose-Diosi collapse model, QBism and of course the exotic Many Worlds theory. Again he shows respect for Bohm and the other theorists but doesn’t buy into their theories. He thinks the theories are important even if they are wrong. They may help find a better path to understanding the quantum by spawning new ideas. He devotes a chapter to Many Worlds which he rejects, not because its implications are bizarre, but because he finds it incoherent.
A good end to this discussion is a parlor game Ball cites. It’s a version of the Twenty Questions. In the normal version the questioner has twenty questions which can only be answered yes or no to discover a word, person or thing the other players have agreed on. In the modified version the other players don’t have a specific thing to be discovered. Rather they agree only to answer questions in a manner consistent with all the previous answers in a way that allows the discovery of something. At the end whatever answer the questioner comes up with is right as long as it is consistent with those answers. It sounds a lot like our investigation of the quantum world. The questions you ask determine what you will find.
Take the issue of wave-particle duality. Ball notes “Quantum objects are not sometimes particles and sometimes waves…we have no reason to suppose that ‘what they are� changes in any meaningful way depending on how we try to look at them. So the phrase ‘wave-particle duality� doesn’t really refer to quantum objects at all, but the interpretation of experiments…� “Einstein expressed it by saying that quantum objects present us with a choice of languages, but it is too easily forgotten that this is precisely what it is: a struggle to formulate the right words, not a description of the reality behind them.�
Erwin Schrodinger developed a wave equation for an electron substituting electrical charge for amplitude, which normal wave equations represent. Ball goes on “It was a natural thing to assume, but it was wrong. The wave in Schrodinger’s wave isn’t a wave of electron charge density. In fact, it’s not a wave that corresponds to any concrete physical property. It is just a mathematical abstraction � for which reason it is not really a wave at all, but is called a wavefunction.� The wavefunction, however, is useful. It can determine probabilities such as finding a quantum object in a particular position or with a particular momentum or energy, depending on the experiment. Ball continues “And - here’s the really important thing � this wavefunction contains all the information one can possibly access about the corresponding quantum particle.� But even though you can get a probability of finding an electron in a particular place, the wavefunction �says nothing about where the electron is.� “The wavefunction is not a description of the entity we call an electron. It is a prescription for what to expect when we make measurements on that entity�. Many physicists would disagree with that statement, but it represents the thinking of Niels Bohr and those that subscribe to the Copenhagen Interpretation.
While Ball accepts that quantum mechanics does not describe an underlying reality, he doesn’t believe that means there isn’t one. However, Ball is not a realist. Most scientists who are realists know that the wavefunction is not a real description of the underlying reality, but believe that it corresponds to an objective reality. After all, what produces the measurements we make? This realist view is the ontic view as opposed to the epistemic view of the Copenhagenists. In the latter view we only get probabilities for the result of our measurements, but can’t even speak of an underlying reality.
The idea of superposition, that a quantum object can be in two or more places or two or more states at the same time runs into arguments similar to those for wave-particle duality. The wavefunction is a solution to Schrodinger’s equation, which like other equations can have multiple solutions which can be combined. These multiple solutions can be considered separate states but it is a matter of interpretation. Ball notes “But strictly speaking a superposition should be considered only as an abstract mathematical thing.� In a normal wave equation another solution is just another wave, but because Schrodinger is using wave physics for quantum states it gets confusing. In Ball’s words “superpositions of quantum states only seem odd because the wavefunctions are used to describe the properties of entities that we can also regard as particles � meaning that such particles seem to be able to have two or more values of their properties at once.�
The double-slit experiment not only seems to show that an electron can take two paths at once like a wave, but that it can switch back to particle behavior taking only one path when observed. There is no explanation for this, but there is no reason to assume that the quantum object actually changes. For more on the double slit experiment I highly recommend reading Anil Ananthaswamy’s Through Two Doors at Once. With descriptions of many types of double slit experiments, he really gets you to appreciate just how strange quantum mechanics is. He shows that not only does a particle appear to take two paths at the same time but seems to go back in time which Ball also alludes to. Feynman’s quantum electrodynamics is sometimes used to support a particle taking multiple paths, but does the mathematics actually represent reality. In the calculations, most paths cancel out. Ball says it is a flat out wrong assumption, �The electron or photon does not take all possible paths.�
Ball thinks Heisenberg’s Uncertainty Principle would be better called the Unknowable Principle. We can’t measure multiple quantum properties at the same time �because they can’t exist all at once. And by gathering some we may scramble the values of others.� The order in which measurements are made makes a difference. Ball points out that measurements of spin components change based on the order. Measuring one scrambles the measurement of the other. Ball gives a very good explanation of “spin�, electron orbits, and quantum numbers that are used to define quantum states. Some variables can be measured accurately at the same time such as mass and charge but others known as conjugate variables have limited accuracy when measured at the same time - the more precise the measurement of one, the less precise the measurement of the other. Position and momentum are conjugate variables as are energy and time. Why these and not others? Ball cannot think of an intuitive explanation, but he says it’s in the math. Heisenberg’s matrix mechanics solution is not commutative for these properties. A times B does not equal B times A. The difference between the calculations is the difference in accuracy of the Uncertainty Principle. Regarding momentum and measurement, momentum in waves is measured by wave length, something not conducive to a precise position measurement. Ball explains this in more detail. Sean Carroll in Something Deeply Hidden also does a very good job of explaining this.
Then there is the issue of entanglement. Ball describes this as quantum objects with shared properties represented by a single wavefunction, even though they may be far distant from each other in space. “As far as quantum mechanics is concerned, entanglement makes them both parts of a single object.� In experiments the spin of entangled electrons isn’t correlated because they communicate with each other, but because the property of spin is non-local in entangled electrons. Ball notes “The main thing you need to know about entanglement is this: it tells us that a quantum object may have properties that are not entirely located on that object.� Some physicists suspect that entanglement is what ties together spacetime. In one model “spacetime and gravity in the 3D universe look like a projection of the entanglement existing within its 2D boundary surface.� Entanglement may also be important to developing a theory of quantum gravity. Carlo Rovelli’s Reality is Not What it Seems gives an accessible description of loop quantum gravity and how spacetime could emerge from the quantum. Rovelli embraces Heisenberg’s matrix solution to quantum mechanics, but sees Schrodinger’s wave function only as an aid to calculation.
Next Ball discusses where the quantum world ends and the classical world begins. It’s not a matter of size. Rather it is a loss of coherence or decoherence. The Schrodinger equation describes quantum objects in terms of abstract waves that determine probabilities. Ball notes “It is this waviness that gives rise to distinctly quantum phenomena like, interference, superposition and entanglement. These behaviours become possible when there is a well-defined relationship between the quantum ‘waves�: in effect when they are in step. This coordination is called coherence.� Without coherence “there can be no regular interference pattern, but just random, featureless variations in the resulting wave amplitude.� When a quantum object encounters another object it becomes entangled with it. Given the abundance of photons, air molecules, dust grains and such in the environment, this entanglement rapidly spreads. The quantum object’s individual superposition is lost when it becomes a part of the wavefunction of the larger object. These classical objects are decoherent and do not display quantum superposition or interference. The classical world grows out of the quantum world. It is not separate from it.
Ball devotes a couple of chapters to quantum computing. The increased speed of quantum computers is commonly ascribed to superposition, accessing more than one state of each qubit. For this the qubits must maintain coherence and not get entangled with their environment. This is a technological challenge, and so far quantum computers have only been able to maintain a small number of qubits in their quantum state for long enough to perform calculations. So it may be a while before quantum computers challenge conventional ones. Ball sees quantum computers as having excellent potential for specific tasks such as factoring large numbers, important to cryptography, and also for large data base searches. He doubts that they will replace your laptop for everyday tasks. He also points out that there are skeptics of the idea that quantum computers achieve their speed through parallel processing due to superposition of the qubits. Rather the increased performance may be due to qubits entangled with each other allowing them to be managed together rather than in separate steps saving time. There are other theories, but no consensus. Ball states point blank that “no one fully understands how quantum computers work.�
Ball analyzes some of the interpretations. Copenhagen is his starting point. He shows great respect for Bohr and much of what he said, but takes exception to the notion that there will never be a way to find out more about the quantum world. From there he looks at the de Broglie-Bohm interpretation, the GRW collapse model, the Penrose-Diosi collapse model, QBism and of course the exotic Many Worlds theory. Again he shows respect for Bohm and the other theorists but doesn’t buy into their theories. He thinks the theories are important even if they are wrong. They may help find a better path to understanding the quantum by spawning new ideas. He devotes a chapter to Many Worlds which he rejects, not because its implications are bizarre, but because he finds it incoherent.
A good end to this discussion is a parlor game Ball cites. It’s a version of the Twenty Questions. In the normal version the questioner has twenty questions which can only be answered yes or no to discover a word, person or thing the other players have agreed on. In the modified version the other players don’t have a specific thing to be discovered. Rather they agree only to answer questions in a manner consistent with all the previous answers in a way that allows the discovery of something. At the end whatever answer the questioner comes up with is right as long as it is consistent with those answers. It sounds a lot like our investigation of the quantum world. The questions you ask determine what you will find.
October 26, 2020
In Beyond Weird, Philip Ball argues that we are undermining and oversimplifying quantum mechanics by calling it weird. It’s something that most of us, the media and even scientists have done. Quantum mechanics is much more than that and it is a disservice to just use such a common and easy way to describe it, for want of better wording. The problem is that we might not have the right words to describe quantum mechanics.
Quantum mechanics is famous for being ambiguous. As a result, it’s one of the areas of science (if not the only one) that is subject to different interpretations. The act of measurement plays a central role in its interpretation. Why is quantum theory probabilistic? What about its lack of causality? And do quantum objects have real properties, just like the ones we see in our classical world, the so-called hidden variables of quantum mechanics, or is the measurement act just a way of getting more knowledge and does it present a limit to our knowledge, represented by the collapse of the wavefunction? Is there some underlying meaning or must we just accept that quantum mechanics is different from any other scientific theory and stop questioning its reality? These and many others were central themes in the arguments that Bohr, Einstein and other physicists had in the past and still have to this day. These two ways of looking at quantum theory represent the ontic and epistemic views, respectively, which remain a debate to this day among physicists.
Philip Ball gives subtle hints of his stance on the meaning of quantum mechanics throughout the book. In the last chapters this subtlety slowly disappears, as his opinions get more fleshed out. I got the impression that he is closer to the Copenhagen and maybe even qbism interpretations, while at the same time dismissing the pilot wave and MWI interpretation (which was a relief to be honest, as there are many physicists out there defending it in a rather “fierce� way). He seems to be a big fan of the role information (its meaning in physics is described in the book) could play in quantum theory (and also in quantum computing). By the end of the book, he argues that we should be able to describe quantum theory in terms of words which have meaning, just like we are able to describe, say, Newton’s laws and Einstein’s relativity, rather than only having an abstract mathematical theory which we don’t really know what it means and gives rise to so much ambiguity and debate.
This a remarkable book about the foundations of quantum mechanics. Anyone from a physicist to a layperson should enjoy it. Philip Ball is a great science writer. He doesn’t shy away from technical terms and considers the reader to be able to understand his reasoning, as he explains the most important topics of quantum mechanics and its possible meanings. Personally, I loved this book with its complete focus on science and would recommend it to anyone interested in knowing why quantum mechanics is indeed beyond weird.
Quantum mechanics is famous for being ambiguous. As a result, it’s one of the areas of science (if not the only one) that is subject to different interpretations. The act of measurement plays a central role in its interpretation. Why is quantum theory probabilistic? What about its lack of causality? And do quantum objects have real properties, just like the ones we see in our classical world, the so-called hidden variables of quantum mechanics, or is the measurement act just a way of getting more knowledge and does it present a limit to our knowledge, represented by the collapse of the wavefunction? Is there some underlying meaning or must we just accept that quantum mechanics is different from any other scientific theory and stop questioning its reality? These and many others were central themes in the arguments that Bohr, Einstein and other physicists had in the past and still have to this day. These two ways of looking at quantum theory represent the ontic and epistemic views, respectively, which remain a debate to this day among physicists.
Philip Ball gives subtle hints of his stance on the meaning of quantum mechanics throughout the book. In the last chapters this subtlety slowly disappears, as his opinions get more fleshed out. I got the impression that he is closer to the Copenhagen and maybe even qbism interpretations, while at the same time dismissing the pilot wave and MWI interpretation (which was a relief to be honest, as there are many physicists out there defending it in a rather “fierce� way). He seems to be a big fan of the role information (its meaning in physics is described in the book) could play in quantum theory (and also in quantum computing). By the end of the book, he argues that we should be able to describe quantum theory in terms of words which have meaning, just like we are able to describe, say, Newton’s laws and Einstein’s relativity, rather than only having an abstract mathematical theory which we don’t really know what it means and gives rise to so much ambiguity and debate.
This a remarkable book about the foundations of quantum mechanics. Anyone from a physicist to a layperson should enjoy it. Philip Ball is a great science writer. He doesn’t shy away from technical terms and considers the reader to be able to understand his reasoning, as he explains the most important topics of quantum mechanics and its possible meanings. Personally, I loved this book with its complete focus on science and would recommend it to anyone interested in knowing why quantum mechanics is indeed beyond weird.
March 15, 2020
I always try to get alternate viewpoints from as many scientists as I can. I also enjoy sorting out my understanding of quantum physics, searching for better stories, better analogies, and just... BETTER. This book is one of the BETTER. It may not be as charming as some and I don't mind how it skimps on biographies and jumps right into the SCIENCE, but it does fall short in outright describing the math. (That may be a good thing for some. Especially if you're not in the mood to crunch math.)
To be certain, this text goes beyond the everyday norm and focuses on the science. The ideas. The concerns. And it's all in the service of demystifying it all.
Quantum Physics is one of those subjects that agrees on fundamental maths but invites wildly divergent theories that make a coherent STORY of our reality. You know: Copenhagen (don't go nuts on us,) Everett (multiple-worlds), String, and more.
What we have in this book is not a biography of the physicists but an admirable attempt to make the famously weird (thank you Feynman!) as commonplace and normal as can be.
I mean, we're human, and humans are most famous for turning all things truly fantastic into the stunningly banal. :)
And this is exactly what this book tries to accomplish. Step by step, it demystifies the very small particles, removes the term spooky action, and naturalizes all things entangled.
It gives time to the various big-action theories that align the quantum with the macro, and all of this is pretty good if not as good as some other books that cover these topics, but what this book does best is describe the current technology of quantum computers. It doesn't shirk the shortcomings of our descriptions or the limitations of the process. This isn't a PR job by prospective companies trying to sell you a 100k computer.
BTW quantum computers ARE on the market now. Some developers are working on cheaper versions. What are they really good at? Factoring prime numbers.
Thank goodness! That's great for all you hackers out there! PGP MAY need a booster soon. :)
While this one doesn't always come close to the charm I'm used to in popularized physics books, I really have nothing bad to say about the contents.
To be certain, this text goes beyond the everyday norm and focuses on the science. The ideas. The concerns. And it's all in the service of demystifying it all.
Quantum Physics is one of those subjects that agrees on fundamental maths but invites wildly divergent theories that make a coherent STORY of our reality. You know: Copenhagen (don't go nuts on us,) Everett (multiple-worlds), String, and more.
What we have in this book is not a biography of the physicists but an admirable attempt to make the famously weird (thank you Feynman!) as commonplace and normal as can be.
I mean, we're human, and humans are most famous for turning all things truly fantastic into the stunningly banal. :)
And this is exactly what this book tries to accomplish. Step by step, it demystifies the very small particles, removes the term spooky action, and naturalizes all things entangled.
It gives time to the various big-action theories that align the quantum with the macro, and all of this is pretty good if not as good as some other books that cover these topics, but what this book does best is describe the current technology of quantum computers. It doesn't shirk the shortcomings of our descriptions or the limitations of the process. This isn't a PR job by prospective companies trying to sell you a 100k computer.
BTW quantum computers ARE on the market now. Some developers are working on cheaper versions. What are they really good at? Factoring prime numbers.
Thank goodness! That's great for all you hackers out there! PGP MAY need a booster soon. :)
While this one doesn't always come close to the charm I'm used to in popularized physics books, I really have nothing bad to say about the contents.
June 26, 2024
The great physicist Ernest Rutherford said, around 1915: "If you can’t explain your physics to the barmaid, it is probably not very good physics."* It's fair to say that Quantum Mechanics/quantum physics (QM) isn't even close to passing the Rutherford Test. But it's getting closer -- and there's hope, says Philip Ball.
Ball has written about as good a popular introduction to QM as anyone could, perhaps because he got his start as a chemist, as did I. And Ball's book has gotten many, many favorable reviews. So, why did it take me 5 months to finish this short book? Not exactly a gripping read! But every other pop-science explanation of QM I've tried to read has been worse. Some a LOT worse. This is likely the best to date. It still has problems -- as the author freely admits. Citing something close to Rutherford's Rule, above.
I particularly like Ball's observation that recapitulating the history of the discovery of QM, as is often done in physics classes, is misleading. And that "quanta" are more a symptom than a cause. "If we named it today, we'd call it something else." QM is about quanta about like Newton's gravity was about comets: inspiration, yes, but hardly the climax! Quanta were "the telltale clue and no more."
And I LOVED Natalie Wolchover's review at Nature, -- with such gems as that the Copenhagen Interpretation � is “shut up and calculate except without ever shutting up." And “Quantum theory had the strangest genesis,� Ball says. “Its pioneers made it up as they went along. What else could they do?�
I just came to "photosynthesis" in my notes, as a good example Ball (and others) cite as an example of QM effects in everyday life. I wrote: Grass is green. Nature is grainy. Leave it at that. OK, that's a bit cryptic.... Just like this topic! And photosynthesis is, well, really hard to understand. I've tried....
The heart of Weird QM remains the Double-Slit experiment, --that demonstrates wave-particle duality, and has been bedeviling students since 1927! All particles exhibit a wave nature. All waves (such as light) exhibit a particulate nature (such as photons). Hey, Einstein struggled with this stuff, too! And it is truly a *weird* result. As you may recall from school.
Ball certainly could have made his book more useful as a reference by adding a TOC [!!] and making a more comprehensive index. Oh, well. I still plan to reread it sometime -- unless something better comes along. Especially if it passes the Rutherford Test!
----------
Notes:
*Actually, he said this several different ways. As did other Famous Physicists, including Einstein! Who probably got it from Rutherford first:
�
The specific review that brought me to read this book was Brian Clegg's at Physics World. And Ball's book won the "Physics World Book of the Year" award for 2018: Clegg's review is linked there.
Ball has written about as good a popular introduction to QM as anyone could, perhaps because he got his start as a chemist, as did I. And Ball's book has gotten many, many favorable reviews. So, why did it take me 5 months to finish this short book? Not exactly a gripping read! But every other pop-science explanation of QM I've tried to read has been worse. Some a LOT worse. This is likely the best to date. It still has problems -- as the author freely admits. Citing something close to Rutherford's Rule, above.
I particularly like Ball's observation that recapitulating the history of the discovery of QM, as is often done in physics classes, is misleading. And that "quanta" are more a symptom than a cause. "If we named it today, we'd call it something else." QM is about quanta about like Newton's gravity was about comets: inspiration, yes, but hardly the climax! Quanta were "the telltale clue and no more."
And I LOVED Natalie Wolchover's review at Nature, -- with such gems as that the Copenhagen Interpretation � is “shut up and calculate except without ever shutting up." And “Quantum theory had the strangest genesis,� Ball says. “Its pioneers made it up as they went along. What else could they do?�
I just came to "photosynthesis" in my notes, as a good example Ball (and others) cite as an example of QM effects in everyday life. I wrote: Grass is green. Nature is grainy. Leave it at that. OK, that's a bit cryptic.... Just like this topic! And photosynthesis is, well, really hard to understand. I've tried....
The heart of Weird QM remains the Double-Slit experiment, --that demonstrates wave-particle duality, and has been bedeviling students since 1927! All particles exhibit a wave nature. All waves (such as light) exhibit a particulate nature (such as photons). Hey, Einstein struggled with this stuff, too! And it is truly a *weird* result. As you may recall from school.
Ball certainly could have made his book more useful as a reference by adding a TOC [!!] and making a more comprehensive index. Oh, well. I still plan to reread it sometime -- unless something better comes along. Especially if it passes the Rutherford Test!
----------
Notes:
*Actually, he said this several different ways. As did other Famous Physicists, including Einstein! Who probably got it from Rutherford first:
�
The specific review that brought me to read this book was Brian Clegg's at Physics World. And Ball's book won the "Physics World Book of the Year" award for 2018: Clegg's review is linked there.
February 19, 2024
I think this book takes a great approach.
It doesn’t just do a layman’s explanation of quantum physics. Instead, it focuses a lot on the problem of quantum physics concepts being so hard to visualize.
We can intuitively understand stuff like gravity, covalent bonds in molecules, cell division etc
But when it comes to stuff like objects can be both waves and particles, they can have multiple positions, Schorindinger’s cat, Heisenberg’s uncertainty principle etc?
We’re just lost. These concepts are just so counter intuitive.
The book addresses it.
Some of this is because the popular media description of these concepts are just completely different from the actual scientific concept.
But most of it - the author explains that it isn’t correct to think in terms of an “underlying reality� as that is a classical physics concept.
(This is apparently actually the dominant model in quantum physics called the Copenhagen interpretation)
Ok, I admit that is also pretty counter intuitive. And I wouldn’t be surprised if my above sentence made no sense at all.
But the author explains it extremely well in this book.
He’s one of the best science writers I’ve come across. And if he can do such an excellent job with the most inaccessible domain of science, I’m sure his other books are excellent.
Already ordered my next Philip Ball book.
It doesn’t just do a layman’s explanation of quantum physics. Instead, it focuses a lot on the problem of quantum physics concepts being so hard to visualize.
We can intuitively understand stuff like gravity, covalent bonds in molecules, cell division etc
But when it comes to stuff like objects can be both waves and particles, they can have multiple positions, Schorindinger’s cat, Heisenberg’s uncertainty principle etc?
We’re just lost. These concepts are just so counter intuitive.
The book addresses it.
Some of this is because the popular media description of these concepts are just completely different from the actual scientific concept.
But most of it - the author explains that it isn’t correct to think in terms of an “underlying reality� as that is a classical physics concept.
(This is apparently actually the dominant model in quantum physics called the Copenhagen interpretation)
Ok, I admit that is also pretty counter intuitive. And I wouldn’t be surprised if my above sentence made no sense at all.
But the author explains it extremely well in this book.
He’s one of the best science writers I’ve come across. And if he can do such an excellent job with the most inaccessible domain of science, I’m sure his other books are excellent.
Already ordered my next Philip Ball book.
November 18, 2021
‘Beyond Weird� is a popular introduction to Quantum Mechanics that is fairly accessible. It covers, among other things, uncertainty, entanglement, superposition, non- locality, measurement, and contextuality. It also explores the major different interpretations and the issues presently being discussed in the field. The whole thing is presented in broad strokes, which actually suited the lacking in a science background me down to the ground. Worth reading if you are interested in the subject.
September 12, 2018
a very good overview of the controversies and theories of the foundation of quantum physics with lots of recent interpretations and experiments that have started to change the "usual" story one reads about (Bohr, Einstein, Heisenberg, Schrodinger etc) in both major and subtle ways
Highly recommended and very readable and accessible without too much math
Highly recommended and very readable and accessible without too much math
Shelved as 'dnf-not-my-cup-of-coffee'
June 1, 2022I loved the beginning so much, and I thought it would become another favorite of mine, And then, I lost all interest. Maybe because it became quite repetitive, or I just got tired of so many "we don't know". Or maybe it's my poor mood (most likely this is it). Anyway, I put a stop at 27%. Perhaps I will pick it up again sometime. But for now, it's a no go for me.
June 15, 2019
For years there was very little published comparing different interpretations of QM. Suddenly there seems to be a flood of them. While I loved by , this one might be even better. Becker was re-telling the history of QM and discussing the personalities of the scientists along with talking about interpretations. Ball skips almost completely over the history and personalities and just gets right down to what we currently know and several attempts at interpretation.
Becker was more friendly to the Many Worlds Interpretation(s) which Ball pretty much considers logically inconsistent. (I share his sentiment, but don't fully follow the argument.) Ball gives much more detail on how "decoherence" could maybe avoid the "measurement problem". And Ball talks about recent ideas on whether "super-quantum entanglement" and "PR boxes" can exist and if not, why not. I'd only met that concept before in a "graphic novel" type book: .
I'm going to have to read this again later to really get my head around it.
There are a few things I hate about this book. The title is horrible and the subtitle is worse. No table of contents. No chapter numbers. End notes are not numbered or linked easily to the page they are commenting on. But despite all that, this is excellent!
Becker was more friendly to the Many Worlds Interpretation(s) which Ball pretty much considers logically inconsistent. (I share his sentiment, but don't fully follow the argument.) Ball gives much more detail on how "decoherence" could maybe avoid the "measurement problem". And Ball talks about recent ideas on whether "super-quantum entanglement" and "PR boxes" can exist and if not, why not. I'd only met that concept before in a "graphic novel" type book: .
I'm going to have to read this again later to really get my head around it.
There are a few things I hate about this book. The title is horrible and the subtitle is worse. No table of contents. No chapter numbers. End notes are not numbered or linked easily to the page they are commenting on. But despite all that, this is excellent!
November 1, 2019
Beyond whatever subject I end up being interested in from time to time, quantum mechanics, the study of the processes that lie at the bottom of reality, is the most interesting subject. If you disagree, you can physically fight me. I tend to come back to books on quantum mechanics from time to time to learn about the recent discoveries, which in a field as bizarre as this one could mean a complete reframing of reality.
This is the kind of book on quantum mechanics you read after you've been hit with most of its mysteries and you have had some time to ponder them. In any case, the nonsensical results of the famous double slit experiment are a good first approximation to the subject, or to get a refresher.
In the double slit experiment, you put a photon gun on one side of a table, a panel in the middle that you can slide revealing either one or two slits, and on the opposite side of the table some sort of "wall" of material that can capture the impression of the photons as they hit it. The experiment progressed in phases through the years:
1) In a single slit configuration, you shoot a bunch of photons at once. On the wall a stripe appears where the photons hit it: the kind of impression produced when a bunch of particles go through a narrow slit behaving like microscopic bullets.
2) In a two slit configuration, after shooting the photons at once, you would expect to get two stripes on the wall, a strip behind each slit, as the particles of light passed through either one slit or the other. That's not what happens. Instead you get something like this on the wall:
That's an interference pattern caused by waves, which is routinely described mathematically. So are particles concrete entities, or are they waves? Both?
3) In a two slit configuration, you use the photon gun so it only fires a single photon after the previous one has hit the wall. Naturally, the photon then would have to pass through one slit or the other, and the final impression on the wall would suggest a particle based nature for the photons. However, that's not what happens: you get the same interference pattern as in the previous point. But a single photon could not interfere with any other, so that must at least mean that it is interfering with itself.
4) To figure out through which of the slits each photon passes, you can put special detectors. In a two slit configuration and with the photon gun shooting plenty at once, as long as there is a detector in any of the slits that doesn't otherwise interact with the photon, what you get on the wall is a particle based behavior: two stripes of impressions. The result changes depending on whether or not you choose to measure the progress midway through. That's a phenomenon unheard of in classical physics, not to mention completely illogical.
5) The scientists got clever and pushed the detector further in between a slit and the wall. A photon would hit it and through the detector you would figure out if it passed through that slit or the other. However, nature would not be tricked: if you try to detect the path of a particle from its origin to the moment it hits the wall, the interference pattern disappears. That would mean that a particle that hits a detector after it passes a slit is able to go back in time or know ahead of time that its properties are going to be measured midway through, and the particle will change how it manifests.
The study of quantum mechanics, even at the level of a layman, implies realizing that the most basic assumptions about reality hold up during your day to day just because that's how the world happens to manifest as at your size. But it's quantum mechanics all the way down, and at some point the following assumptions break down: that there's a history of cause and effect you can follow, that an object has a solid physical presence with defined properties, that the properties of an object will not change depending on how you look at it, that all the properties of an object will be located in that object, and not, lets say, light years away, that measuring the properties of an object repeatedly doesn't change the results or even invalidate some property, etc.
The revelations of quantum mechanics strike us as illogical and contrary to common sense, but only because our instincts and intelligence are not attuned to reality as it is: we evolved to handle the world from the ground to the height of some lowest branches, and that's all we ever needed. It's so bad that even putting the behaviors discovered through quantum mechanics in words in a coherent manner is very hard, because it hits the limits of what human language is able to express.
Although quantum mechanics is a field that started in the early 20th century, there's still no orthodoxy about some of its biggest mysteries: turns out that at the bottom of reality everything comes down to something called a wavefunction, a mathematical representation of the probabilities a quantum object's properties will have this or that value when measured. For example, an electron "trapped" in a box, when measured could have a 95 percent probability of being found inside the solid box, but a non-negligible probability of being found inside the walls of the box, or even outside of it. This phenomenon, called quantum tunneling, is used extensively in electronics to exchange electrons between its elements; around 30% of the world's economy depends on applied quantum mechanics. The controversy regarding wavefunctions comes down to two factions: one of them believes that the wavefunction relates to an underlying physical reality with a history of cause and effect, but the other position, so far backed by more evidence, says that asking what exists "under" the wavefunction doesn't make sense, because the properties of a quantum object manifest when measured: literally come into existence. The phenomenon of radioactivity is evidence for this position, because radioactive decay seems to be truly random.
Probably my favorite quantum behavior is that of entanglement: two quantum objects can be "interlinked" so as to the properties of one become part of the other. If an entangled electron spins, you know that its paired electron will have spun in the opposite direction. That's how reality works. The astonishing issue is that the linked effect will happen immediately, no matter how far away one quantum object is from the other, even light years away. This happens with no apparent physical connection of any kind transmiting information between them. Obviously the phenomenon breaks the speed of light, which should be impossible. It suggests that the distances in spacetime are illusory, and that all the points are in fact connected. That's some hope for someone like me who wishes we would be able to "move" faster than light to other planets. However, some scientists seem to believe that in fact the effects of entanglement don't break the speed of light, because the correlation between the measurement of one of the pairs and the other, to make sure that they have changed, will always be made at the speed of light. I'm not sure if I can understand that; it seems to me that the effect would have happened anyway already, but part of quantum mechanics is that the effects don't "pop up" into existence until measured. So it's another head spin.
Learning about behaviors like these makes many students of quantum mechanics shiver with the notion that reality is in fact a computer simulation (likely in a quantum computer). Anyone who programs complicated graphic simulations knows that only what's going to appear on the screen (therefore to be looked at) is really represented and drawn, and everything else is just variables waiting to be transformed into a representation when their turn on the stage comes. If you were to write a simulation that someone would experience, having all of the entities' properties as a range of probabilities to be spawned when someone would require that experience is likely the least resource intensive way of simulating an entire universe, because the underlying memory wouldn't have to keep precise track of anything nobody is paying attention to. That's very suspicious. So is entanglement in that case: how you would store the coordinates of the entire universe would have no relation to its physical representation, and therefore there would be no problem with manipulating linked entities at the same time.
The notion that depending on how you choose to observe nature at its rawest you get different results, often even contradictory, and therefore consciousness seemed to be able to change reality, has seeped over the decades into the public perception, in nasty ways. One of the worst recent examples is an idea I won't name that seemed to become most popular amongst isolated housewives: that what the universe creates depends on your thoughts, which often means that positive thoughts result in the universe gifting you whatever you wished for (and if your kid ended up developing an aggressive cancer, you weren't positive enough). However, over the recent decades the role of consciousness has been taken out of the picture entirely, and we now understand how a quantum system becomes "classical". A quantum system starts "coherent", with all its possible states in superpositions, but through interactions with the environment, the system "decoheres". It's not the action of measuring, but the interaction between the macroscopic measuring devices and the coherent quantum system. Some quantum states "blur out" faster than others, and/or are more resistant to interference. However, you don't seem to be able to choose which of the possibilities the system's wavefunction (in this case an aggregation of wavefunctions) collapses to. The size of the elements of a quantum system does matter, because the more atoms it contains the higher the risk of a catastrophic interaction, but experiments have shown that there seems to be no limit to the size of an object to sustain it in a quantum state, as long as you isolate it from enviromental influences and cool it down "enough".
It's important to restate this: there's no gap between the quantum world and the classical world. The classical world is the result of smudged out quantum states, and there are ways to keep them coherent perpetually, and in some cases even recover decohered states.
Far from being a curiosity, this breakthrough has been used in the development of quantum computers. We are used to hearing the adjective "quantum" attached to any name in order for it to sound futuristic, but quantum computers are entirely based on quantum mechanics. They were first proposed, officially at least, by physicist Richard Feynman: he brought to the world's attention that the computers that were being developed were based on classical physics, which would be unable to simulate nor bring solutions to the most complicated and time consuming problems that could be turned into algorithms: to realistically simulate any physical system, it should be processed in quantum states to its smallest element, because that's how reality works, but so far our computers had only been able to produce approximations very, very distant from how the universe actually works.
The average person would think that our current classical computers are fast enough. If you are a programmer and into artificial intelligence, you know that training a neural network requires from hours to days and sometimes even weeks. However, none of that comes close to the amount of time required by the most meaningful problems. Finding out new ways for proteins to fold could lead to enormous advances in medicine and biology in general, but the permutations involving realistic amounts of atoms and molecules are far too high for computers to handle. Finding entirely new materials, for example, is a process that throughout human history has been more a matter of luck than a deliberate process, and yet a quantum computer could try an insane number of permutations of realistically simulated atoms. The advances that could come in the field of artificial intelligence are unimaginable. Something as simple in theory as evolving the entire structure of a vehicle, down to the atomic level, so it adjusts through billions of iterations to the requirements wanted by a company (for example speed, stability, resistance, etc.) could be achieved in seconds.
Some of the top scientists, employed by some of the most important companies, have been competing to achieve the holy grail: quantum supremacy. They defined it as the moment when an algorithm that would take a known amount of time in a supercomputer to solve would be invariably solved much faster in a quantum computer. After some hesitation, Google recently announced that they had achieved that breakthrough. The following link is for their video: . The test they devised would have taken a supercomputer 10,000 years to process. The complex problems mentioned before are on those realms of intractable time. Their quantum computer spat out the correct result in little more than three minutes. It solved in three minutes a problem that would have taken 10,000 years with our previous best technology.
It's very hard to predict what's going to happen from now on. A major hurdle is figuring out the quantum algorithm to describe a problem; if you can't program it in, the quantum computer can't even attempt to process it. Who knows if most problems that are handled by classical computers are going to be translatable to quantum computers, or if the quantum computers of the future will end up taking up space in our houses; after all, the quantum bits need to be isolated from their environment and cooled to near absolute zero. But remember that some of the problems that a quantum computer would be able to solve is discovering new materials.
There isn't a field whose developments I follow more closely than quantum computing. For me this feels like we are jumping from the bronze age to the space age. A worrying aspect of it, of course, is that human beings, the primates with delusions of grandeur that we are, aren't known to handle breakthrough technological advances in a very rational, peaceful manner.
This is the kind of book on quantum mechanics you read after you've been hit with most of its mysteries and you have had some time to ponder them. In any case, the nonsensical results of the famous double slit experiment are a good first approximation to the subject, or to get a refresher.
In the double slit experiment, you put a photon gun on one side of a table, a panel in the middle that you can slide revealing either one or two slits, and on the opposite side of the table some sort of "wall" of material that can capture the impression of the photons as they hit it. The experiment progressed in phases through the years:
1) In a single slit configuration, you shoot a bunch of photons at once. On the wall a stripe appears where the photons hit it: the kind of impression produced when a bunch of particles go through a narrow slit behaving like microscopic bullets.
2) In a two slit configuration, after shooting the photons at once, you would expect to get two stripes on the wall, a strip behind each slit, as the particles of light passed through either one slit or the other. That's not what happens. Instead you get something like this on the wall:
That's an interference pattern caused by waves, which is routinely described mathematically. So are particles concrete entities, or are they waves? Both?
3) In a two slit configuration, you use the photon gun so it only fires a single photon after the previous one has hit the wall. Naturally, the photon then would have to pass through one slit or the other, and the final impression on the wall would suggest a particle based nature for the photons. However, that's not what happens: you get the same interference pattern as in the previous point. But a single photon could not interfere with any other, so that must at least mean that it is interfering with itself.
4) To figure out through which of the slits each photon passes, you can put special detectors. In a two slit configuration and with the photon gun shooting plenty at once, as long as there is a detector in any of the slits that doesn't otherwise interact with the photon, what you get on the wall is a particle based behavior: two stripes of impressions. The result changes depending on whether or not you choose to measure the progress midway through. That's a phenomenon unheard of in classical physics, not to mention completely illogical.
5) The scientists got clever and pushed the detector further in between a slit and the wall. A photon would hit it and through the detector you would figure out if it passed through that slit or the other. However, nature would not be tricked: if you try to detect the path of a particle from its origin to the moment it hits the wall, the interference pattern disappears. That would mean that a particle that hits a detector after it passes a slit is able to go back in time or know ahead of time that its properties are going to be measured midway through, and the particle will change how it manifests.
The study of quantum mechanics, even at the level of a layman, implies realizing that the most basic assumptions about reality hold up during your day to day just because that's how the world happens to manifest as at your size. But it's quantum mechanics all the way down, and at some point the following assumptions break down: that there's a history of cause and effect you can follow, that an object has a solid physical presence with defined properties, that the properties of an object will not change depending on how you look at it, that all the properties of an object will be located in that object, and not, lets say, light years away, that measuring the properties of an object repeatedly doesn't change the results or even invalidate some property, etc.
The revelations of quantum mechanics strike us as illogical and contrary to common sense, but only because our instincts and intelligence are not attuned to reality as it is: we evolved to handle the world from the ground to the height of some lowest branches, and that's all we ever needed. It's so bad that even putting the behaviors discovered through quantum mechanics in words in a coherent manner is very hard, because it hits the limits of what human language is able to express.
Although quantum mechanics is a field that started in the early 20th century, there's still no orthodoxy about some of its biggest mysteries: turns out that at the bottom of reality everything comes down to something called a wavefunction, a mathematical representation of the probabilities a quantum object's properties will have this or that value when measured. For example, an electron "trapped" in a box, when measured could have a 95 percent probability of being found inside the solid box, but a non-negligible probability of being found inside the walls of the box, or even outside of it. This phenomenon, called quantum tunneling, is used extensively in electronics to exchange electrons between its elements; around 30% of the world's economy depends on applied quantum mechanics. The controversy regarding wavefunctions comes down to two factions: one of them believes that the wavefunction relates to an underlying physical reality with a history of cause and effect, but the other position, so far backed by more evidence, says that asking what exists "under" the wavefunction doesn't make sense, because the properties of a quantum object manifest when measured: literally come into existence. The phenomenon of radioactivity is evidence for this position, because radioactive decay seems to be truly random.
Probably my favorite quantum behavior is that of entanglement: two quantum objects can be "interlinked" so as to the properties of one become part of the other. If an entangled electron spins, you know that its paired electron will have spun in the opposite direction. That's how reality works. The astonishing issue is that the linked effect will happen immediately, no matter how far away one quantum object is from the other, even light years away. This happens with no apparent physical connection of any kind transmiting information between them. Obviously the phenomenon breaks the speed of light, which should be impossible. It suggests that the distances in spacetime are illusory, and that all the points are in fact connected. That's some hope for someone like me who wishes we would be able to "move" faster than light to other planets. However, some scientists seem to believe that in fact the effects of entanglement don't break the speed of light, because the correlation between the measurement of one of the pairs and the other, to make sure that they have changed, will always be made at the speed of light. I'm not sure if I can understand that; it seems to me that the effect would have happened anyway already, but part of quantum mechanics is that the effects don't "pop up" into existence until measured. So it's another head spin.
Learning about behaviors like these makes many students of quantum mechanics shiver with the notion that reality is in fact a computer simulation (likely in a quantum computer). Anyone who programs complicated graphic simulations knows that only what's going to appear on the screen (therefore to be looked at) is really represented and drawn, and everything else is just variables waiting to be transformed into a representation when their turn on the stage comes. If you were to write a simulation that someone would experience, having all of the entities' properties as a range of probabilities to be spawned when someone would require that experience is likely the least resource intensive way of simulating an entire universe, because the underlying memory wouldn't have to keep precise track of anything nobody is paying attention to. That's very suspicious. So is entanglement in that case: how you would store the coordinates of the entire universe would have no relation to its physical representation, and therefore there would be no problem with manipulating linked entities at the same time.
The notion that depending on how you choose to observe nature at its rawest you get different results, often even contradictory, and therefore consciousness seemed to be able to change reality, has seeped over the decades into the public perception, in nasty ways. One of the worst recent examples is an idea I won't name that seemed to become most popular amongst isolated housewives: that what the universe creates depends on your thoughts, which often means that positive thoughts result in the universe gifting you whatever you wished for (and if your kid ended up developing an aggressive cancer, you weren't positive enough). However, over the recent decades the role of consciousness has been taken out of the picture entirely, and we now understand how a quantum system becomes "classical". A quantum system starts "coherent", with all its possible states in superpositions, but through interactions with the environment, the system "decoheres". It's not the action of measuring, but the interaction between the macroscopic measuring devices and the coherent quantum system. Some quantum states "blur out" faster than others, and/or are more resistant to interference. However, you don't seem to be able to choose which of the possibilities the system's wavefunction (in this case an aggregation of wavefunctions) collapses to. The size of the elements of a quantum system does matter, because the more atoms it contains the higher the risk of a catastrophic interaction, but experiments have shown that there seems to be no limit to the size of an object to sustain it in a quantum state, as long as you isolate it from enviromental influences and cool it down "enough".
It's important to restate this: there's no gap between the quantum world and the classical world. The classical world is the result of smudged out quantum states, and there are ways to keep them coherent perpetually, and in some cases even recover decohered states.
Far from being a curiosity, this breakthrough has been used in the development of quantum computers. We are used to hearing the adjective "quantum" attached to any name in order for it to sound futuristic, but quantum computers are entirely based on quantum mechanics. They were first proposed, officially at least, by physicist Richard Feynman: he brought to the world's attention that the computers that were being developed were based on classical physics, which would be unable to simulate nor bring solutions to the most complicated and time consuming problems that could be turned into algorithms: to realistically simulate any physical system, it should be processed in quantum states to its smallest element, because that's how reality works, but so far our computers had only been able to produce approximations very, very distant from how the universe actually works.
The average person would think that our current classical computers are fast enough. If you are a programmer and into artificial intelligence, you know that training a neural network requires from hours to days and sometimes even weeks. However, none of that comes close to the amount of time required by the most meaningful problems. Finding out new ways for proteins to fold could lead to enormous advances in medicine and biology in general, but the permutations involving realistic amounts of atoms and molecules are far too high for computers to handle. Finding entirely new materials, for example, is a process that throughout human history has been more a matter of luck than a deliberate process, and yet a quantum computer could try an insane number of permutations of realistically simulated atoms. The advances that could come in the field of artificial intelligence are unimaginable. Something as simple in theory as evolving the entire structure of a vehicle, down to the atomic level, so it adjusts through billions of iterations to the requirements wanted by a company (for example speed, stability, resistance, etc.) could be achieved in seconds.
Some of the top scientists, employed by some of the most important companies, have been competing to achieve the holy grail: quantum supremacy. They defined it as the moment when an algorithm that would take a known amount of time in a supercomputer to solve would be invariably solved much faster in a quantum computer. After some hesitation, Google recently announced that they had achieved that breakthrough. The following link is for their video: . The test they devised would have taken a supercomputer 10,000 years to process. The complex problems mentioned before are on those realms of intractable time. Their quantum computer spat out the correct result in little more than three minutes. It solved in three minutes a problem that would have taken 10,000 years with our previous best technology.
It's very hard to predict what's going to happen from now on. A major hurdle is figuring out the quantum algorithm to describe a problem; if you can't program it in, the quantum computer can't even attempt to process it. Who knows if most problems that are handled by classical computers are going to be translatable to quantum computers, or if the quantum computers of the future will end up taking up space in our houses; after all, the quantum bits need to be isolated from their environment and cooled to near absolute zero. But remember that some of the problems that a quantum computer would be able to solve is discovering new materials.
There isn't a field whose developments I follow more closely than quantum computing. For me this feels like we are jumping from the bronze age to the space age. A worrying aspect of it, of course, is that human beings, the primates with delusions of grandeur that we are, aren't known to handle breakthrough technological advances in a very rational, peaceful manner.
May 28, 2024
Quantum theory, which deals with the world at its smallest-known scale, always gives me the feeling that someone somewhere is cheating, sort of moving the goalposts about to suit themselves. First it means one thing, then it means something else (except when it doesn’t of course), and so on. But I also know that that’s because I haven’t understood it. Beyond Weird is an attempt at setting straight all the misconceptions there are about this subject, and in particular the greatest one of all, namely, that things down at the sub-atomic level are “weird�. That’s what “Beyond Weird� means: not “even stranger than weird�, but rather, getting past the idea that it’s weird at all and seeing that, in fact, it’s anything but.
For a start, the writing here is exceptional, so clear and comprehensible it’s almost as if the guy is sitting in a chair opposite you explaining it in person—one of the best pieces of science-writing I’ve come across. It’s non-mathematical, yet goes into real depth (and is up to date too, or 2019 at least). Also, unlike so many other books on the subject, this is not so much an exhaustive round-up of the details, but more about their interpretation overall, how on earth we make some kind of sense of them. Such as: that quantum objects can be both waves and particles; can simultaneously be both here and there; can affect one another instantly across vast distances; and that you can’t observe them without changing them. “Quantum mechanics might seem ‘weird�, but it is not illogical. It’s just that it employs a new and unfamiliar logic. If you can grasp it…then the quantum world may stop seeming weird and become just another place, with different customs and traditions and with its own beautiful internal consistency…�
And above all: “Such ‘paradoxes� apparently permit the answers Yes and No simultaneously. Whatever we are to make of that, we must surely aspire to do better than shrug and call it ‘weird�.�
For a start, the writing here is exceptional, so clear and comprehensible it’s almost as if the guy is sitting in a chair opposite you explaining it in person—one of the best pieces of science-writing I’ve come across. It’s non-mathematical, yet goes into real depth (and is up to date too, or 2019 at least). Also, unlike so many other books on the subject, this is not so much an exhaustive round-up of the details, but more about their interpretation overall, how on earth we make some kind of sense of them. Such as: that quantum objects can be both waves and particles; can simultaneously be both here and there; can affect one another instantly across vast distances; and that you can’t observe them without changing them. “Quantum mechanics might seem ‘weird�, but it is not illogical. It’s just that it employs a new and unfamiliar logic. If you can grasp it…then the quantum world may stop seeming weird and become just another place, with different customs and traditions and with its own beautiful internal consistency…�
And above all: “Such ‘paradoxes� apparently permit the answers Yes and No simultaneously. Whatever we are to make of that, we must surely aspire to do better than shrug and call it ‘weird�.�
December 11, 2021
I am not gifted mathematically. It confounds me. Always has. Always will. However, that doesn't diminish my fascination with some theories. Which annoys me to no end! I don't understand quantum physics on a level that smarty pants folk do...;-) but from just my own little perspective it makes sense to me. I actually sometimes use it as a mind game "when I'm bored." It's probable possibilities are astounding to me. I remember when I first heard about the string theory, and I thought "well, let's check this out." Took me about 6 month's to decide it was B.S. Ah, but the quantum thing...It's possibilities are mind boggling, "to me anyway." This book is definitely readable. By that, I mean it's readable for those of us who aren't scientists, or mathematically inclined. See, I'm not religious, but I like to think that there's "something." This works well for me. My thanks to the publishers and Netgalley for letting me read and review this fairly awesome book! I greatly enjoyed it.
September 10, 2024
I think that’s the best book I’ve read on the attempts to explain the apparent weirdness associated with Quantum Mechanics, the scientific framework used to model and describe the subatomic world (and some larger scales too).
That doesn’t mean it was an easy read. My head is spinning a bit from what I’ve taken in over a few days of intensive reading. This is a book for people who have an interest and some understanding on the physics of the subatomic; if you pricked up your ears when you heard about the Higgs Boson (though it’s not discussed here). There’s no maths, no equations, but you probably should have a vague understanding of physics, heard of the uncertainty principle and Schrodinger’s Cat. Maybe not be complete strangers to the scientists (e.g. Bohr, Einstein and Heisenberg) who developed the concepts 100 years ago. There’s plenty of background given, but it’s not a complete beginners book to quantum mechanics.
The author starts by explaining why anyone, including those who developed it, would find the observations of the subatomic world, and the possible explanations, weird: objects that appear to behave both as waves and particles; probability appears to play a part in what you observe in experiments; you need equations with a thing called a ‘wave function� (which no one really understands) to model results in experiments though these usually turn out to be incredibly accurate. Despite our best and often successful attempts to model this weird world with our maths we’re still not sure if we can simply explain it, how to visualise things at this level.
The idea that our brain evolved to observe and understand everyday phenomena, but struggles with concepts outside of that, isn’t new. Our perceptions and language colour the questions we can ask of the world and what we can understand from it. “It’s me not you�, when we get confused looking at a subatomic world, where everyday analogies we often use to explain things collapse. Even for atomic physics I recall from my college days that modelling atoms in a gas as little billiard balls bouncing off of each other explains pretty much everything you’d want to know about gas behaviours (“kinetic theory of gases�); even if atoms plainly aren’t mini billiard balls the analogy, for physical behaviour, isn’t bad in giving an understanding. When we go down a level to the subatomic world things get much harder to understand.
The author explores this territory in detail, and well. He gives the best explanation of Bell’s Theorem I've read, which has led to critical modern era experiments that show quantum physics truly is weird at its basic level, and not because ‘real information� is hidden from us by some subatomic fog. The still strange ‘Two Slits� experiment is further explored.
He looks at the philosophical side, the attempts to give meaning to the observations, even if most really are exercises in semantics, offering no tests to show they’re better than others. Overall he appears to favour the ‘Copenhagen Interpretation� and sticks the boot into the fashionable ‘Many Worlds� approach and probably persuaded me on that, although he’s refreshingly undogmatic with his assessments. Quite a bit on decoherence, the process where the quantum world blends into our macro world. I’m not that familiar with it. Interesting but some of the ideas expressed will need chewing on, for me.
Most of the above is outlined in the first 50-60% of the book. Thereafter it gets a little unstructured with a long review of quantum computing and its possibilities, and interestingly he’s not particularly positive about its benefits. There’s some vague stuff about reformulating the basics of quantum mechanics away from that of Schrödinger and Heisenberg into an information theory approach but I didn’t really follow how that’d make more sense.
It finishes strongly with a review of what he’s looked at and reminds us that physics as a whole isn’t in a mess as a result of all this apparent quantum level confusion. Nature gets on with its job reliably everyday, and in the macro world we can model and understand it well. Our macro world has this strange quantum world underlying it but here the weirder effects are suppressed by collections of millions and billions of particles interacting together. Even in the subatomic world we seem to have a mathematical language in place that gives good predictions - it’s just that here we find it hard to put into everyday explanations what we observe in experiments and why. Maybe that’s as far as we can get?! Our language and that which the universe works with are just too different?
Good mind stretching enjoyment. But my ageing brain cells now need a bit of a rest from science for a while. Highly recommended to the popular science brigade with some basic physics interests. 5*.
That doesn’t mean it was an easy read. My head is spinning a bit from what I’ve taken in over a few days of intensive reading. This is a book for people who have an interest and some understanding on the physics of the subatomic; if you pricked up your ears when you heard about the Higgs Boson (though it’s not discussed here). There’s no maths, no equations, but you probably should have a vague understanding of physics, heard of the uncertainty principle and Schrodinger’s Cat. Maybe not be complete strangers to the scientists (e.g. Bohr, Einstein and Heisenberg) who developed the concepts 100 years ago. There’s plenty of background given, but it’s not a complete beginners book to quantum mechanics.
The author starts by explaining why anyone, including those who developed it, would find the observations of the subatomic world, and the possible explanations, weird: objects that appear to behave both as waves and particles; probability appears to play a part in what you observe in experiments; you need equations with a thing called a ‘wave function� (which no one really understands) to model results in experiments though these usually turn out to be incredibly accurate. Despite our best and often successful attempts to model this weird world with our maths we’re still not sure if we can simply explain it, how to visualise things at this level.
The idea that our brain evolved to observe and understand everyday phenomena, but struggles with concepts outside of that, isn’t new. Our perceptions and language colour the questions we can ask of the world and what we can understand from it. “It’s me not you�, when we get confused looking at a subatomic world, where everyday analogies we often use to explain things collapse. Even for atomic physics I recall from my college days that modelling atoms in a gas as little billiard balls bouncing off of each other explains pretty much everything you’d want to know about gas behaviours (“kinetic theory of gases�); even if atoms plainly aren’t mini billiard balls the analogy, for physical behaviour, isn’t bad in giving an understanding. When we go down a level to the subatomic world things get much harder to understand.
The author explores this territory in detail, and well. He gives the best explanation of Bell’s Theorem I've read, which has led to critical modern era experiments that show quantum physics truly is weird at its basic level, and not because ‘real information� is hidden from us by some subatomic fog. The still strange ‘Two Slits� experiment is further explored.
He looks at the philosophical side, the attempts to give meaning to the observations, even if most really are exercises in semantics, offering no tests to show they’re better than others. Overall he appears to favour the ‘Copenhagen Interpretation� and sticks the boot into the fashionable ‘Many Worlds� approach and probably persuaded me on that, although he’s refreshingly undogmatic with his assessments. Quite a bit on decoherence, the process where the quantum world blends into our macro world. I’m not that familiar with it. Interesting but some of the ideas expressed will need chewing on, for me.
Most of the above is outlined in the first 50-60% of the book. Thereafter it gets a little unstructured with a long review of quantum computing and its possibilities, and interestingly he’s not particularly positive about its benefits. There’s some vague stuff about reformulating the basics of quantum mechanics away from that of Schrödinger and Heisenberg into an information theory approach but I didn’t really follow how that’d make more sense.
It finishes strongly with a review of what he’s looked at and reminds us that physics as a whole isn’t in a mess as a result of all this apparent quantum level confusion. Nature gets on with its job reliably everyday, and in the macro world we can model and understand it well. Our macro world has this strange quantum world underlying it but here the weirder effects are suppressed by collections of millions and billions of particles interacting together. Even in the subatomic world we seem to have a mathematical language in place that gives good predictions - it’s just that here we find it hard to put into everyday explanations what we observe in experiments and why. Maybe that’s as far as we can get?! Our language and that which the universe works with are just too different?
Good mind stretching enjoyment. But my ageing brain cells now need a bit of a rest from science for a while. Highly recommended to the popular science brigade with some basic physics interests. 5*.
June 14, 2018
I was a bit hesitant about reading this book initially as I thought who needs yet another popular science book about quantum mechanics or the history of quantum mechanics. I decided to pick up a copy as Jim Al-Khalili gave it a glowing review.
The good news is that this isn't just another history of quantum mechanics, but a great up to date account of where quantum theory is today. There is a lot of focus on the interpretation of QM from Many Worlds, Copenhagen Interpretation etc. through to modern ideas around quantum information and quantum computing.
This is a really interesting read, but it isn't necessarily an easy read (coming from someone who did two quantum mechanics courses at degree level and two quantum field theory courses at masters level). It should appeal to mathematicians and physicists, but I would recommend the layperson reads the excellent first.
The good news is that this isn't just another history of quantum mechanics, but a great up to date account of where quantum theory is today. There is a lot of focus on the interpretation of QM from Many Worlds, Copenhagen Interpretation etc. through to modern ideas around quantum information and quantum computing.
This is a really interesting read, but it isn't necessarily an easy read (coming from someone who did two quantum mechanics courses at degree level and two quantum field theory courses at masters level). It should appeal to mathematicians and physicists, but I would recommend the layperson reads the excellent first.
July 22, 2020
This is a book that tries to describe the weirdness of quantum mechanics. And I think it does a great job. Although it is written primarily for the general audience, I don't recommend it if you're not familiar with the ABC of QM. There are much simpler books out there.
Quantum mechanics doesn’t tell us how a thing is, but what (with calculable probability) it could be, along with � and this is crucial � a logic of the relationships between those ‘coulds�. If this, then that.
What this means is that, to truly describe the features of quantum mechanics, as far as that is currently possible, we should replace all the conventional ‘isms� with ‘ifms�. For example:
Not
‘here it is a particle, there it is a wave�
but
‘if we measure things like this, the quantum object behaves in a manner we associate with particles; but if we measure it like that, it behaves as if it’s a wave�
Not
‘the particle is in two states at once�
but
‘if we measure it, we will detect this state with probability X, and that state with probability Y�
Quantum mechanics doesn’t tell us how a thing is, but what (with calculable probability) it could be, along with � and this is crucial � a logic of the relationships between those ‘coulds�. If this, then that.
What this means is that, to truly describe the features of quantum mechanics, as far as that is currently possible, we should replace all the conventional ‘isms� with ‘ifms�. For example:
Not
‘here it is a particle, there it is a wave�
but
‘if we measure things like this, the quantum object behaves in a manner we associate with particles; but if we measure it like that, it behaves as if it’s a wave�
Not
‘the particle is in two states at once�
but
‘if we measure it, we will detect this state with probability X, and that state with probability Y�
July 1, 2024
Asombrosa síntesis, muy equilibrada en sus apreciaciones de las distintas interpretaciones de la Cuántica, incluye muchos datos (teoremas, paradojas, conjeturas) que no he leído en otros textos sobre el tema, muy completo el capítulo dedicado a la de coherencia cuántica.
Diría que es la mejor visión panorámica que, alguien *ya* informado del tema, puede obtener del estado actual de la discusión sobre los fundamentos de la Cuántica.
Aunque tengo más de 4 libros de Phillip Ball este es el primero que leo de este prolijo autor de divulgación científica. Me ha gustado mucho su estilo entre pragmático, asequible pero también sin temor a profundizar cuando se hace necesario.
Muy bueno el estilo de capítulos cortos con notas al final de cada capítulo.
Reseña en extenso en cocción.
Diría que es la mejor visión panorámica que, alguien *ya* informado del tema, puede obtener del estado actual de la discusión sobre los fundamentos de la Cuántica.
Aunque tengo más de 4 libros de Phillip Ball este es el primero que leo de este prolijo autor de divulgación científica. Me ha gustado mucho su estilo entre pragmático, asequible pero también sin temor a profundizar cuando se hace necesario.
Muy bueno el estilo de capítulos cortos con notas al final de cada capítulo.
Reseña en extenso en cocción.
February 9, 2019
Well, I like it, but should I recommend it?
It really depends. If you are just curious intellectually then go ahead and check it out. It's not very easy though, after all you are trying to learn quantum physics. But it's manageable. That's an incredible feat that the author was able to achieve. I have zero background in quantum physics, though do work with probability. But Philip Ball speaks in such an intelligible language (despite him repeatedly saying the limit of language in expressing quantum ideas), without refering much if at all to math.
I appreciate that some physicists in particular (and reasearchers in all fields in general) do care about the "meaning(s)" of of math and their experiments. It's also fun philosophically, as people still struggle with the implications and interpretations of quantum physics. It's an open ended question and you, by the end of the book, kind of participate in that discussion too. Which side do you take? I dislike the many worlds theory too, but not completely sold by the information theory one.
The book is almost purely intellectual (except for a short discussion about computing, very cool indeed). There is no conclusion yet because it's still an intense debate, and you will only vaguely grasp a tiny bit of quantum physics. Whether it's worth your time, it's up to you.
It really depends. If you are just curious intellectually then go ahead and check it out. It's not very easy though, after all you are trying to learn quantum physics. But it's manageable. That's an incredible feat that the author was able to achieve. I have zero background in quantum physics, though do work with probability. But Philip Ball speaks in such an intelligible language (despite him repeatedly saying the limit of language in expressing quantum ideas), without refering much if at all to math.
I appreciate that some physicists in particular (and reasearchers in all fields in general) do care about the "meaning(s)" of of math and their experiments. It's also fun philosophically, as people still struggle with the implications and interpretations of quantum physics. It's an open ended question and you, by the end of the book, kind of participate in that discussion too. Which side do you take? I dislike the many worlds theory too, but not completely sold by the information theory one.
The book is almost purely intellectual (except for a short discussion about computing, very cool indeed). There is no conclusion yet because it's still an intense debate, and you will only vaguely grasp a tiny bit of quantum physics. Whether it's worth your time, it's up to you.
June 25, 2018
I had high hopes for a Philip Ball quantum book as he's a good and original pop science writer. The fact I didn't get on too well with it is probably because he pours super-cooled water on the multiple worlds interpretation, as well as some of the other famously strange bits of quantum physics. Not knowing the maths or actually being a physicist of any kind I've got no way of sensibly deciding whether he's wrong or not, of course (though as far as I can make out he has a chiefly hypocritical reason for discounting it - he says that a sort of aesthetic outrage against infinite universes being created at every quantum junction is not a valid reason for denying the MWI; half a page later, he seems to be saying a similar kind of outrage at the creation of infinite minds within those universes is why the MWI is unthinkable). But let's face it, infinite universes are much more fun for the lay reader to think about, so you're always going to come across a little curmudgeonly if you attack them.
November 14, 2019
Took me a while to finish this book. It’s a reasonably good summary of what’s known and mostly what’s unknown about quantum mechanics. A bit too long and a bit repetitive. For me, the most important discovery was the notion/interpretation of QBism which I wasn’t aware of until now.
January 26, 2020
This is not a review of the book - the book is fantastic with new insights pouring out in every section and with nary a word wasted. The rest of the writeup is an extended summary of my takeaways for whatever they are worth.
Beyond Weird makes one think more than almost any other book on the subject. This reviewer has read dozens of books on quantum physics over the last two decades. For years, I have been swayed by, and against, different interpretations. Like any amateur, my impressions were roughly set by the last thing I read.
For the first time, I have my own view. Three caveats before I get into it:
I am an amateur. I do not have the language rigor or practice to explain what I feel precisely.
My views are shaped mainly by the book again, which happens to be the last one I read! Unlike before, I have my modifications/hypothesis. I am astounded by how much more is known or almost proven about the decoherence. I am also impressed by the book's counters against the other popular schools of thought, particularly the Copenhagen interpretation as well as the many-world.
I retain that quantum mechanics and interactions are not fully comprehensible in anything other than their raw equations. Interpretations sought any other way, particularly through natural languages, materially reduce its explicatory powers, if not lead to substantial errors.
Finally, to my complete picture (a lot of it is derived from the author's beliefs in the book): All physical entities have quantum nature or quantumness. Schrodinger's equations give us a description of this quantum potential nature. These aspects of physical entities are probabilistic with particular randomness built-in, and humanity is yet to unearth it completely. The quantumness of any system is more apparent when it is reasonably small and allowed to operate in isolation.
Physical entities' quantumness interact with each other when they come in close connections with each other. The quantumness entanglement is over and above what we know about influences through the classical forces. Let's say there is a new "force," called quantum force (QF), to describe these interactions or entanglements involving the quantumness of the entities. QF is made up by me to understand quantum behavior and unlikely to be a real force in the traditional sense. That said, I so dream some QF-like to be the source of dark energy!
Effectively, when quantum characteristics of different physical entities interfere with each other, some of the quantumness - particularly in the "direction" of the most robust interaction - fuse like two waves of different wavelengths. Combinations of differing wave functions, like interference of unharmonious waves, causes decoherence. As the book details, this decoherence is no longer a theory: some of it is well measured, including its pace and extent in quantum experiments.
There is more to it: while a decoherence happens in one or more directions or dimensions of strongest intermingling, the entities continue to have quantumness in many other parts, albeit altered. One can argue that if a previous decoherence had eliminated the quantumness in one direction/dimension, call it A, a new entanglement along B would recreate quantumness ("recoherence"?) along A.
When the extent of decoherence - because of the strength of QF - is exceptionally substantial in any dimension, it would appear like a collapse of quantumness in that dimension/parameter and emergence of a classical manifestation.
My artificial QF to explain decoherence is an ultra short-range force. It looks like its impact is proportional to the "size" of the elements involved, which would explain the quick collapse caused by macro devices and/or the environment in the double slit.
In other words, decoherence or collapse is measured on the smaller of the interacting elements as the quantumness of the larger elements is too faint and is even more faintly impacted by the smaller elements (Penrose may be onto something with the gravity hypothesis).
Quantum scientists need to study this interaction frontier or the entanglement, and the associated decoherences more as it might unearth a lot more. For example, I feel that while a collapse happens in one/some directions of a quantum interaction, the quantumness is preserved and re-created in the "non-aligned" (poorly defined by me) directions.
Let me elaborate on this: no environment seems to obliterate the quantumness of any element in all directions/dimensions. Decoherence appears to happen only along some parameters. Perhaps, the total quantumness of any system is always constant - so now we got a preservation law too! Or quantumness is only partially destroyed and is re-creatable. This is the reason why the universe still has particles exhibiting quantumness, and we did not have a complete collapse into everything classical at the Big Bang.
So take the usual Stern-Gerlach experiment: a set of particles that pass through the z-axis filter interact with the environment such that a strong z-axis interaction leaves them polarised either up or down along the z-axis (pointer state). If measured again along the same axis, those with the up result the first time keep showing up and vice versa. Effectively, these particles' z-axis spin (einstate) has decohered and assumed a fixed value but not spin along any other axis. If the next environmental element causes decoherence along any other axis, the z-axis decoherence is lost (i.e., it gets scrambled or reobtains quantumness in its z-axis spin).
We can rephrase what we have been explained more simplistically through the Heisenberg's. As per the uncertainty principle, the more one fixes the position, the less one can know about the momentum. Generalizing it, it seems the more one decoheres in one dimension, the less one does in many other (maybe all other) conjugal dimensions.
The decoherence interpretation almost entirely explains the impact of the observation, which is nothing but introduction of an environment or elements that cause quantum interactions. Like in the relativity, the frame of reference matters in this line of thinking. The reference frame is different, as it is more about elements introduced to make the measurement and the decoherence they enforce. This is the reason why what matters depends on what questions are asked. There is nothing that seems to be absolute in quantum theory, either.
Let's stretch this further. We know nothing about the quantumness interactions today. It is possible that as we understand them more, we might even be able to answer "why this and not that." It is conceivable that just like those myriads of unknown elements or forces that cause a standing pin to fall in one direction or not the other, we may have a quantum version of the same through interactions.
Finally, I know what I believe in, at least as of today. As the author says, such interpretations are more a reflection of the believers' biases and leanings than whatever might be the reality. There is no compulsion for the reality to be of any human-conceived idea mold.
That said, intuitive leaps of faith have helped the quantum science progress right from its inceptions. Major insights developed by Einstein (quantum nature of photons), Bohr (quantized orbits of the electron), Heisenberg (uncertainty principle), Bohm (probability imputation), Schrodinger's wave function were all well-judged guesses or hypothesis that made massive contributions to the field. Could it be the same for QF?!!
Well, that's enough about my views based on what I understood. Let me also note some other well-made points in the book for future reference.
Quantization, or the world being grainy at the smallest level, is a small part or effect of the quantum theory. Quantum theory is not because of the quantized nature of matter and energy but the other way around. In other words, nothing is staggering about the quantized nature by itself except that that is how the world is.
The author beautifully summarises Susskind's views about where quantum mechanics is different from the classical. For most of us, the difference has something to do with the fact that the classical world is analog/continuous. At the same time, the base reality seems to be digital and discontinuous - quantum. The author/Susskind feels that this is not a big deal. Quantum theory has an entirely different mathematical abstraction or representation of the fundamental particles.
Consequently, one obtains a comprehensively different type of abstraction or mathematical equation sets for their interactions with each other too. In quantum mechanics, there is a relationship between the state of the system and any measurements made on it. This implies that the equations on the state of the system are not enough until we decide where we want to deploy them (or how we want to measure) as there is not much reality without measurement.
The book does well in its refutations of both the Copenhagen and the many-world notions. The descriptions are particularly enlightening when the author writes about quantum mechanics as an epistemic versus an ontic theory. The believers of its epistemic nature view the theory, and its components like wave function, as prescriptive. They are artificial constructs that help us forecast what we are likely to obtain if we make some measurements on the underlying system and nothing more or less. The Copenhagen interpretation is such an epistemic view.
The ontic view is that QM equations (or its better future variants) are descriptive of the underlying reality the way classical parameters like density or temperature are. The epistemic believers generally do not like "why" questions or in-depth interpretations of the theory and are more of a "shut up" and calculate variety.
The author does equally well in demystifying the classical, macro world we observe versus the underlying world of the particles. The former can be an emergent phenomenon of the latter as we have more reasons to believe in the decoherence. As we understand quantum entanglements/interactions better, we might even find answers to why this and not that (i.e., why we get one reality and not some other with a quantum collapse). This could be the best refutation of the many-world; the author does well in rebuffing it as a usable theory. That is, it adds little to our understanding even while extending the theoretical scope materially more without anything provable.
The short book has useful sections on quantum computing as well. The section on how little is understood about quantum interactions and the end results from the gate-like conversions of qubits is most important. It highlights the need for science to focus on the decoherence. As we learn more about decoherence, quantum computing could make astounding progress, particularly if it is accompanied by a better ability to manipulate quantum states as well.
Beyond Weird makes one think more than almost any other book on the subject. This reviewer has read dozens of books on quantum physics over the last two decades. For years, I have been swayed by, and against, different interpretations. Like any amateur, my impressions were roughly set by the last thing I read.
For the first time, I have my own view. Three caveats before I get into it:
I am an amateur. I do not have the language rigor or practice to explain what I feel precisely.
My views are shaped mainly by the book again, which happens to be the last one I read! Unlike before, I have my modifications/hypothesis. I am astounded by how much more is known or almost proven about the decoherence. I am also impressed by the book's counters against the other popular schools of thought, particularly the Copenhagen interpretation as well as the many-world.
I retain that quantum mechanics and interactions are not fully comprehensible in anything other than their raw equations. Interpretations sought any other way, particularly through natural languages, materially reduce its explicatory powers, if not lead to substantial errors.
Finally, to my complete picture (a lot of it is derived from the author's beliefs in the book): All physical entities have quantum nature or quantumness. Schrodinger's equations give us a description of this quantum potential nature. These aspects of physical entities are probabilistic with particular randomness built-in, and humanity is yet to unearth it completely. The quantumness of any system is more apparent when it is reasonably small and allowed to operate in isolation.
Physical entities' quantumness interact with each other when they come in close connections with each other. The quantumness entanglement is over and above what we know about influences through the classical forces. Let's say there is a new "force," called quantum force (QF), to describe these interactions or entanglements involving the quantumness of the entities. QF is made up by me to understand quantum behavior and unlikely to be a real force in the traditional sense. That said, I so dream some QF-like to be the source of dark energy!
Effectively, when quantum characteristics of different physical entities interfere with each other, some of the quantumness - particularly in the "direction" of the most robust interaction - fuse like two waves of different wavelengths. Combinations of differing wave functions, like interference of unharmonious waves, causes decoherence. As the book details, this decoherence is no longer a theory: some of it is well measured, including its pace and extent in quantum experiments.
There is more to it: while a decoherence happens in one or more directions or dimensions of strongest intermingling, the entities continue to have quantumness in many other parts, albeit altered. One can argue that if a previous decoherence had eliminated the quantumness in one direction/dimension, call it A, a new entanglement along B would recreate quantumness ("recoherence"?) along A.
When the extent of decoherence - because of the strength of QF - is exceptionally substantial in any dimension, it would appear like a collapse of quantumness in that dimension/parameter and emergence of a classical manifestation.
My artificial QF to explain decoherence is an ultra short-range force. It looks like its impact is proportional to the "size" of the elements involved, which would explain the quick collapse caused by macro devices and/or the environment in the double slit.
In other words, decoherence or collapse is measured on the smaller of the interacting elements as the quantumness of the larger elements is too faint and is even more faintly impacted by the smaller elements (Penrose may be onto something with the gravity hypothesis).
Quantum scientists need to study this interaction frontier or the entanglement, and the associated decoherences more as it might unearth a lot more. For example, I feel that while a collapse happens in one/some directions of a quantum interaction, the quantumness is preserved and re-created in the "non-aligned" (poorly defined by me) directions.
Let me elaborate on this: no environment seems to obliterate the quantumness of any element in all directions/dimensions. Decoherence appears to happen only along some parameters. Perhaps, the total quantumness of any system is always constant - so now we got a preservation law too! Or quantumness is only partially destroyed and is re-creatable. This is the reason why the universe still has particles exhibiting quantumness, and we did not have a complete collapse into everything classical at the Big Bang.
So take the usual Stern-Gerlach experiment: a set of particles that pass through the z-axis filter interact with the environment such that a strong z-axis interaction leaves them polarised either up or down along the z-axis (pointer state). If measured again along the same axis, those with the up result the first time keep showing up and vice versa. Effectively, these particles' z-axis spin (einstate) has decohered and assumed a fixed value but not spin along any other axis. If the next environmental element causes decoherence along any other axis, the z-axis decoherence is lost (i.e., it gets scrambled or reobtains quantumness in its z-axis spin).
We can rephrase what we have been explained more simplistically through the Heisenberg's. As per the uncertainty principle, the more one fixes the position, the less one can know about the momentum. Generalizing it, it seems the more one decoheres in one dimension, the less one does in many other (maybe all other) conjugal dimensions.
The decoherence interpretation almost entirely explains the impact of the observation, which is nothing but introduction of an environment or elements that cause quantum interactions. Like in the relativity, the frame of reference matters in this line of thinking. The reference frame is different, as it is more about elements introduced to make the measurement and the decoherence they enforce. This is the reason why what matters depends on what questions are asked. There is nothing that seems to be absolute in quantum theory, either.
Let's stretch this further. We know nothing about the quantumness interactions today. It is possible that as we understand them more, we might even be able to answer "why this and not that." It is conceivable that just like those myriads of unknown elements or forces that cause a standing pin to fall in one direction or not the other, we may have a quantum version of the same through interactions.
Finally, I know what I believe in, at least as of today. As the author says, such interpretations are more a reflection of the believers' biases and leanings than whatever might be the reality. There is no compulsion for the reality to be of any human-conceived idea mold.
That said, intuitive leaps of faith have helped the quantum science progress right from its inceptions. Major insights developed by Einstein (quantum nature of photons), Bohr (quantized orbits of the electron), Heisenberg (uncertainty principle), Bohm (probability imputation), Schrodinger's wave function were all well-judged guesses or hypothesis that made massive contributions to the field. Could it be the same for QF?!!
Well, that's enough about my views based on what I understood. Let me also note some other well-made points in the book for future reference.
Quantization, or the world being grainy at the smallest level, is a small part or effect of the quantum theory. Quantum theory is not because of the quantized nature of matter and energy but the other way around. In other words, nothing is staggering about the quantized nature by itself except that that is how the world is.
The author beautifully summarises Susskind's views about where quantum mechanics is different from the classical. For most of us, the difference has something to do with the fact that the classical world is analog/continuous. At the same time, the base reality seems to be digital and discontinuous - quantum. The author/Susskind feels that this is not a big deal. Quantum theory has an entirely different mathematical abstraction or representation of the fundamental particles.
Consequently, one obtains a comprehensively different type of abstraction or mathematical equation sets for their interactions with each other too. In quantum mechanics, there is a relationship between the state of the system and any measurements made on it. This implies that the equations on the state of the system are not enough until we decide where we want to deploy them (or how we want to measure) as there is not much reality without measurement.
The book does well in its refutations of both the Copenhagen and the many-world notions. The descriptions are particularly enlightening when the author writes about quantum mechanics as an epistemic versus an ontic theory. The believers of its epistemic nature view the theory, and its components like wave function, as prescriptive. They are artificial constructs that help us forecast what we are likely to obtain if we make some measurements on the underlying system and nothing more or less. The Copenhagen interpretation is such an epistemic view.
The ontic view is that QM equations (or its better future variants) are descriptive of the underlying reality the way classical parameters like density or temperature are. The epistemic believers generally do not like "why" questions or in-depth interpretations of the theory and are more of a "shut up" and calculate variety.
The author does equally well in demystifying the classical, macro world we observe versus the underlying world of the particles. The former can be an emergent phenomenon of the latter as we have more reasons to believe in the decoherence. As we understand quantum entanglements/interactions better, we might even find answers to why this and not that (i.e., why we get one reality and not some other with a quantum collapse). This could be the best refutation of the many-world; the author does well in rebuffing it as a usable theory. That is, it adds little to our understanding even while extending the theoretical scope materially more without anything provable.
The short book has useful sections on quantum computing as well. The section on how little is understood about quantum interactions and the end results from the gate-like conversions of qubits is most important. It highlights the need for science to focus on the decoherence. As we learn more about decoherence, quantum computing could make astounding progress, particularly if it is accompanied by a better ability to manipulate quantum states as well.
April 21, 2021
Hay que reconocer el esfuerzo del autor por intentar hacer comprensibles los conceptos de la mecánica cuántica y conseguirlo con éxito. Recorrido de una parte de la física, una muy rara, desde el principio a la actualidad que merece la pena si se está interesado en el tema. Deje afuera la lógica causal, aconsejo.
January 10, 2025
A bit complex
March 14, 2019
Mr. Ball provided the lay reader, me, an excellent distillation of the current frontiers in quantum physics, something of a second derivative to the underlying research in the field. Nary an equation appears; even the chapter titles are free of numerical ordering. And what from it?
Mr. Ball capably reviewed the principal themes and characters involved in quantum physics today. We met Messrs. Schrödinger, Bohr, Planck, Heisenberg, Feynman, et alia. We read of entanglement, superposition, collapsing wavefunctions, decoherence, a Many Worlds Interpretation, etc. Then there was that famous cat and even some kittens.
Because Mr. Ball is writing in the vernacular, he permits a line of thought to develop that begins with theory and observation and extends to philosophy. What is reality? How should we process causality? My understanding, now having read this work, is rather more unsettled in reply to those questions. To the firm answers associated with classical physics, quantum physics offers uncertainties, uncertainties that may very well never be satisfactorily resolved. I do also wonder whether we have met an experimental boundary, where theories can no longer be tested against observed natural phenomena because the measurement scales now defy the boundaries of engineering, to the extent measurements can even be made in light of the wily nature of the quantum world.
Mr. Ball capably reviewed the principal themes and characters involved in quantum physics today. We met Messrs. Schrödinger, Bohr, Planck, Heisenberg, Feynman, et alia. We read of entanglement, superposition, collapsing wavefunctions, decoherence, a Many Worlds Interpretation, etc. Then there was that famous cat and even some kittens.
Because Mr. Ball is writing in the vernacular, he permits a line of thought to develop that begins with theory and observation and extends to philosophy. What is reality? How should we process causality? My understanding, now having read this work, is rather more unsettled in reply to those questions. To the firm answers associated with classical physics, quantum physics offers uncertainties, uncertainties that may very well never be satisfactorily resolved. I do also wonder whether we have met an experimental boundary, where theories can no longer be tested against observed natural phenomena because the measurement scales now defy the boundaries of engineering, to the extent measurements can even be made in light of the wily nature of the quantum world.
November 15, 2018
This is, I think, the book on quantum mechanics I've been wanting to read for 15 years—though my ability to embrace it may be due to my experience with the less-comprehensive titles I've read in the meantime. Superb, even if I did get snarled once or twice in Ball's explanations of experiments.
Interesting, though, how many shades of Kant and Wittgenstein I kept encountering. I'm not sure if that's because they've greatly influenced quantum physicists, Ball, or if I just saw them because I love them so much (in true what-I-measure-affects-what-I-see quantum style).
I also had the thought whilst reading that instead of us measuring the universe, perhaps the universe is measuring us...and trying all the time to tell us what it sees in ways we can comprehend.
Interesting, though, how many shades of Kant and Wittgenstein I kept encountering. I'm not sure if that's because they've greatly influenced quantum physicists, Ball, or if I just saw them because I love them so much (in true what-I-measure-affects-what-I-see quantum style).
I also had the thought whilst reading that instead of us measuring the universe, perhaps the universe is measuring us...and trying all the time to tell us what it sees in ways we can comprehend.
January 8, 2019
I found this disappointing. The overall tone is off-putting as Ball condescends to historical figures and oversells the extent to wish decoherence answers outstanding questions in QM. (E.g., as far as I understand, the interpretation makes no unique, testable predictions.). Ball's self-promotional slant steers him away from going into any topic too deeply and instead we get a lot of repetition of a few reductive ideas. One is left wondering how constructive much of the "foundations" work being done really is.
August 2, 2018
A refreshing new angle for me. Great that it took us through to current thinking and was about the ideas and not the personalities. Learned a lot about superposition, entanglement and decoherence - at least in flashes - way beyond my understanding in most ways but a very satisfying and interesting read. I definitely want more of these up to date books as the subject evolves.
Shelved as 'gave-up-on'
January 18, 2019Will this be it? Will this be the book that finally, truly explains quantum physics in laymans terms, so that a even a dunce like me can follow along ?
May 7, 2020
After reading these ~350 pages I now feel like I know less about Quantum Mechanics (QM) than before I started. There were times when some of the concepts were beyond my comprehension (e.g. Popescu-Rohrlich boxes) but hopefully with some more reading and research, I'll be able to understand them.
Ball starts to say, fundamentally that the crux of QM is that measurement on a system affects the outcome of measurements on the system itself. Quantization is not a requirement for QM. The book did solve a long held mystery of mine. How did Schrödinger come up his famous, eponymous, wave equation. He took the equation for waves and tweaked it using intuition, to what he thought would apply to particles. Miraculously it worked. Squaring the wavefunction of an object gives you the probability of finding the object at a given position when measured. QM is often misunderstood as a theory governing things only very small. However, entanglement shows that quantum effects can propagate over vast distances (non-locality).
Schrödinger's cat, commonly misunderstood, is dispelled with swiftly in many ways. Firstly, in the way that Tegmark explains, the cat will die if in a vacuum, otherwise it'll interfere with air molecules (the environment) and decohere and no longer exhibit quantum effects (wavefunctions of macroscopic objects can't interfere or exist in a superposition if they aren't coherent). Further, the notion of a superposition of dead and alive states is meaningless, unless we define what they mean in quantum terms and then calculate the wavefunction. As an aside, Ball explains that superpositions aren't fragile. As they "decohere" their quantumness spreads out into the environment creating a large entity. System and environment merge into a single superposition. This effectively destroys the superposition as we can't discern it anymore by looking at a small part of it.
Interestingly, physicists are actually trying to do this experiment dubbed Schrödinger's Kittens, albeit with much smaller matter - water bears (think around mesoscale/millimeters).
QM teaches us that the order in which we do things (e.g. measurements) matters (non-commutable) dubbed Quantum Contextuality. In classical physics it doesn't matter. This partly explains the double slit experiment, you are in effect doing two different experiments to elicit a classical or quantum outcome. In terms of the uncertainty principle, this explains why we get the results we do. You can't know all the details of a quantum system, the more you measure, the more it will decohere. Until eventually it behaves as a classical system only.
The Many Worlds Interpretation (MWI), was devised as a way to deal with apparent wave function collapse and where it goes afterwards. So now you've created an even bigger problem, of a parallel universe, rather than the smaller problem of wavefunction "collapse". Ball says the MWI is false because it cannot deal with the transfer of consciousness (to other "yous") after universe splitting, as it depends on user experience. Arguments I find more compelling are as follows: science has always told us that the very fine details don't matter and they should hardly be splitting universes. Proponents of MWI feel uncomfortable with proposals such as, Quantum Russian Roulette (if MWI is correct they shouldn't). Finally for me personally, we can't do an experiment to prove MWI correct, so it is unscientific in this regard. MWI does not tell us how the splitting occurs, only that it does.
I was pleasantly surprised to find several pages devoted to quantum computing (QC). Ball says that QC won't necessarily revolutionise home computing. Although they may solve P=NP type problems quicker, breaking current encryption methods easily, they wouldn't really speed up things modern computers already do well. QC is a long way off anyway, currently they can just about find prime factors of 21. It was interesting to learn how they worked.
Ultimately, Ball concludes QM is a theory about the representation and manipulation of information. Further, that the theory needs rewriting from the bottom up (Quantum Reconstruction) so that it's not about waves or particles. That if you start with a few fundamental rules, properties do emerge that describe behaviour of quantum objects.
Concluding, Ball condenses QM down to 3 axioms:
1. You can't transmit information faster than light (no-signalling)
2. You can't deduce or perfectly copy the information in an unknown quantum state (no-cloning)
3. There is no unconditionally secure bit commitment (relating to cryptography)
Much of the problems talking about QM come from language. In that, we lack the vocabulary to accurately describe properties of quantum objects. We have to borrow words such as spin and entanglement.
Ball starts to say, fundamentally that the crux of QM is that measurement on a system affects the outcome of measurements on the system itself. Quantization is not a requirement for QM. The book did solve a long held mystery of mine. How did Schrödinger come up his famous, eponymous, wave equation. He took the equation for waves and tweaked it using intuition, to what he thought would apply to particles. Miraculously it worked. Squaring the wavefunction of an object gives you the probability of finding the object at a given position when measured. QM is often misunderstood as a theory governing things only very small. However, entanglement shows that quantum effects can propagate over vast distances (non-locality).
Schrödinger's cat, commonly misunderstood, is dispelled with swiftly in many ways. Firstly, in the way that Tegmark explains, the cat will die if in a vacuum, otherwise it'll interfere with air molecules (the environment) and decohere and no longer exhibit quantum effects (wavefunctions of macroscopic objects can't interfere or exist in a superposition if they aren't coherent). Further, the notion of a superposition of dead and alive states is meaningless, unless we define what they mean in quantum terms and then calculate the wavefunction. As an aside, Ball explains that superpositions aren't fragile. As they "decohere" their quantumness spreads out into the environment creating a large entity. System and environment merge into a single superposition. This effectively destroys the superposition as we can't discern it anymore by looking at a small part of it.
Interestingly, physicists are actually trying to do this experiment dubbed Schrödinger's Kittens, albeit with much smaller matter - water bears (think around mesoscale/millimeters).
QM teaches us that the order in which we do things (e.g. measurements) matters (non-commutable) dubbed Quantum Contextuality. In classical physics it doesn't matter. This partly explains the double slit experiment, you are in effect doing two different experiments to elicit a classical or quantum outcome. In terms of the uncertainty principle, this explains why we get the results we do. You can't know all the details of a quantum system, the more you measure, the more it will decohere. Until eventually it behaves as a classical system only.
The Many Worlds Interpretation (MWI), was devised as a way to deal with apparent wave function collapse and where it goes afterwards. So now you've created an even bigger problem, of a parallel universe, rather than the smaller problem of wavefunction "collapse". Ball says the MWI is false because it cannot deal with the transfer of consciousness (to other "yous") after universe splitting, as it depends on user experience. Arguments I find more compelling are as follows: science has always told us that the very fine details don't matter and they should hardly be splitting universes. Proponents of MWI feel uncomfortable with proposals such as, Quantum Russian Roulette (if MWI is correct they shouldn't). Finally for me personally, we can't do an experiment to prove MWI correct, so it is unscientific in this regard. MWI does not tell us how the splitting occurs, only that it does.
I was pleasantly surprised to find several pages devoted to quantum computing (QC). Ball says that QC won't necessarily revolutionise home computing. Although they may solve P=NP type problems quicker, breaking current encryption methods easily, they wouldn't really speed up things modern computers already do well. QC is a long way off anyway, currently they can just about find prime factors of 21. It was interesting to learn how they worked.
Ultimately, Ball concludes QM is a theory about the representation and manipulation of information. Further, that the theory needs rewriting from the bottom up (Quantum Reconstruction) so that it's not about waves or particles. That if you start with a few fundamental rules, properties do emerge that describe behaviour of quantum objects.
Concluding, Ball condenses QM down to 3 axioms:
1. You can't transmit information faster than light (no-signalling)
2. You can't deduce or perfectly copy the information in an unknown quantum state (no-cloning)
3. There is no unconditionally secure bit commitment (relating to cryptography)
Much of the problems talking about QM come from language. In that, we lack the vocabulary to accurately describe properties of quantum objects. We have to borrow words such as spin and entanglement.
Entanglement could be the key to the long-standing mystery of how to reconcile quantum mechanics with he theory of gravitation as supplied by general relativity
Not
‘here it is a particle, there it is a wave�
but
‘if we measure things like this, the quantum object behaves in a manner we associate with particles; but if we measure it like that, it behaves as if it’s a wave�
Not
‘the particle is in two states at once�
but
‘if we measure it, we will detect this state with probability X, and that state with probability Y�
What the MWI really denies is the existence of facts at all. It replaces them with an experience of pseudo-facts (we think that this happened, even though that happened too). In so doing, it eliminates any coherent notion of what we can experience, or have experienced, or are experiencing right now. We might reasonably wonder if there is any value � any meaning � in what remains, and whether the sacrifice has been worth it
When someone explains something in a complicated way, it’s often a sign that they don’t really understand it. A popular maxim in science used to be that you can’t claim to understand your subject until you can explain it to your grandmother.
The key difference between classical and quantum mechanics is that the first calculates trajectories of objects while the second calculates probabilities (expressed as a wave equation)
November 3, 2019
Not a physicist by any means, but I've read about Quantum Physics earlier. However, this book explains the arcane concepts of duality, superposition and entanglement in much simpler language. If you are into gathering information about quantum, this is a great book to start with. There aren't many equations, though I would've been okay with a few more of those in the book.
Some deeply-thought provoking statements in the book:
"Quantum objects are not sometimes particles and sometimes waves. Quantum objects are what they are, and we have no reason to suppose that ‘what they are� changes in any meaningful way depending on how we try to look at them."
"Everything that seems strange about quantum mechanics comes down to measurement."
"What is more fundamental � a fact established by logic or one established by observation?"
Is measurement the limit of our understanding of the macro-world? I'm guessing I'm constrained by my senses of what this world is and how it works. Had my senses been different or even just more sensitive, I probably would've seen a very different world.
After reading this book, I'm in state of both understanding and not understanding Quantum Physics at the same time. But if someone "measures" my knowledge about this, decoherence hits and I'll realize I don't know much about it!
Some deeply-thought provoking statements in the book:
"Quantum objects are not sometimes particles and sometimes waves. Quantum objects are what they are, and we have no reason to suppose that ‘what they are� changes in any meaningful way depending on how we try to look at them."
"Everything that seems strange about quantum mechanics comes down to measurement."
"What is more fundamental � a fact established by logic or one established by observation?"
Is measurement the limit of our understanding of the macro-world? I'm guessing I'm constrained by my senses of what this world is and how it works. Had my senses been different or even just more sensitive, I probably would've seen a very different world.
After reading this book, I'm in state of both understanding and not understanding Quantum Physics at the same time. But if someone "measures" my knowledge about this, decoherence hits and I'll realize I don't know much about it!
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