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The Quantum Divide: Why Schrodinger's Cat is Either Dead or Alive
Using a selection of key experiments performed over the past 30 years or so, we present a discussion of the strikingly counter-intuitive phenomena of the quantum world that defy explanation in terms of everyday "common sense" reasoning, and we provide the corresponding quantum mechanical explanations with a very elementary use of associated formalism. Most, but certainly not all, of the experiments we describe are optical experiments involving a very small number of photons (particles of light). We begin with experiments on the wave-particle duality of electrons, proceed to experiments on the particle nature of light and single photon interference, delayed choice experiments and interaction-free detection, then go on to experiments involving the interference of two photons, quantum entanglement and Bell's Theorem, quantum teleportation, large-scale quantum effects and the divide between the classical and quantum worlds, addressing the question as to whether or not there is such a
divide.
divide.
- GenresSciencePhysicsNonfiction
197 pages, Hardcover
First published January 24, 2013
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May 14, 2024Judge :
- Silence ! We are here today to decide the fate of Mr. Schrödinger's cat, who has been accused of being both alive and dead, at the same time, in violation of the laws of nature. Mr. Schrödinger, how do you plead ?
Schrödinger :
- Not guilty, your honor. This is a misunderstanding. I never put my cat in a box with a radioactive source and à poison flask. It was just a thought experiment to illustrate the absurdity of quantum mechanics.
Judge :
- A thought experiment ? So you are saying that your cat is not in a superposition of states, but rather in a definite state of being either alive or dead ?
Schrödinger :
- Yes, that is correct.
Judge :
- Then why don't you open the box and show us ?
Schrödinger :
- Well...I can't do that, your honor.
Judge :
- Why ?
Schrödinger :
- Because opening the box would collapse the wave function and change the outcome of the experiment.
Judge :
- But you just said it was not an experiment, but a thought experiment.
Schrödinger :
- Yes, but it is still based on the principles of quantum mechanics, which are valid for any system, regardless of its size.
Judge :
- So you are saying that your cat is both alive and dead until you open the box and observe it ?
Schrödinger :
- No. I am saying that my cat is in a state of indeterminacy, where it has no definite properties, until I open the box and measure it.
Judge :
-That sounds like a contradiction to me...
Schrödinger :
- It is not a contradiction, your honor, it is a paradox.
Judge :
- A paradox ? What is the difference ?
Schrödinger :
- A contradiction is a statement that is false by logic, while a paradox is a statement that is true by logic, but false by intuition.
Judge :
- And which one is your cat ?
Schrödinger :
- My cat is a paradox, your honor.
Judge :
- I see...And how do you propose to resolve this paradox ?
Schrödinger :
- Well, there are several possible ways to interpret it, your honor.
For example, one could adopt the many-worlds interpretations, which states that every time a quantum measurement is made, the universe splits into multiple branches, where each branch corresponds to a possible outcome. In that case, my cat is alive in one branch and dead in another, and I am also split into two versions, one who sees a live cat, and one who sees a dead cat.
Judge :
- That sounds like hell....
Schrödinger :
- Quite so, your honor. Another option is to adopt the quantum decoherence theory, wich states that the interaction of à quantum system with its environment causes it to lose its coherence and become classical. In that case, my cat is not in a superposition of states, but rather in a mixture of states, where it is either alive or dead with some probability, depending on the environmental factors.
Judge :
- That's more resonable...
Schrödinger :
- It is, your honor. A third option is to adopt the quantum Zeno effect, which states that the frequent observation of à quantum system prevents it from changing its state. In that case, my cat is alive, because I have been constantly checking on it.
Judge :
- Well, Mr. Schrödinger, you already gave me a huge headache...I hereby declare your cat to be alive, and grant it bail, on the condition that you never put it in a box again, without making some holes in it.
Case dismissed.
- Silence ! We are here today to decide the fate of Mr. Schrödinger's cat, who has been accused of being both alive and dead, at the same time, in violation of the laws of nature. Mr. Schrödinger, how do you plead ?
Schrödinger :
- Not guilty, your honor. This is a misunderstanding. I never put my cat in a box with a radioactive source and à poison flask. It was just a thought experiment to illustrate the absurdity of quantum mechanics.
Judge :
- A thought experiment ? So you are saying that your cat is not in a superposition of states, but rather in a definite state of being either alive or dead ?
Schrödinger :
- Yes, that is correct.
Judge :
- Then why don't you open the box and show us ?
Schrödinger :
- Well...I can't do that, your honor.
Judge :
- Why ?
Schrödinger :
- Because opening the box would collapse the wave function and change the outcome of the experiment.
Judge :
- But you just said it was not an experiment, but a thought experiment.
Schrödinger :
- Yes, but it is still based on the principles of quantum mechanics, which are valid for any system, regardless of its size.
Judge :
- So you are saying that your cat is both alive and dead until you open the box and observe it ?
Schrödinger :
- No. I am saying that my cat is in a state of indeterminacy, where it has no definite properties, until I open the box and measure it.
Judge :
-That sounds like a contradiction to me...
Schrödinger :
- It is not a contradiction, your honor, it is a paradox.
Judge :
- A paradox ? What is the difference ?
Schrödinger :
- A contradiction is a statement that is false by logic, while a paradox is a statement that is true by logic, but false by intuition.
Judge :
- And which one is your cat ?
Schrödinger :
- My cat is a paradox, your honor.
Judge :
- I see...And how do you propose to resolve this paradox ?
Schrödinger :
- Well, there are several possible ways to interpret it, your honor.
For example, one could adopt the many-worlds interpretations, which states that every time a quantum measurement is made, the universe splits into multiple branches, where each branch corresponds to a possible outcome. In that case, my cat is alive in one branch and dead in another, and I am also split into two versions, one who sees a live cat, and one who sees a dead cat.
Judge :
- That sounds like hell....
Schrödinger :
- Quite so, your honor. Another option is to adopt the quantum decoherence theory, wich states that the interaction of à quantum system with its environment causes it to lose its coherence and become classical. In that case, my cat is not in a superposition of states, but rather in a mixture of states, where it is either alive or dead with some probability, depending on the environmental factors.
Judge :
- That's more resonable...
Schrödinger :
- It is, your honor. A third option is to adopt the quantum Zeno effect, which states that the frequent observation of à quantum system prevents it from changing its state. In that case, my cat is alive, because I have been constantly checking on it.
Judge :
- Well, Mr. Schrödinger, you already gave me a huge headache...I hereby declare your cat to be alive, and grant it bail, on the condition that you never put it in a box again, without making some holes in it.
Case dismissed.
February 26, 2013
Broadly speaking, science books are either popular science or textbooks. The popular science book is aimed at a general audience with little or no science background required and fills in the basics in a far more interesting way than science was every taught at school. The textbook does the business of educating with the theories, while not worrying too much about the historical context, with readability always coming a distant second. It assumes the reader has science and maths education to the required level. But The Quantum Divide, perhaps in keeping with the concept of quantum superposition, manages to be a bit of both at the same time.
What we have here is an exploration of quantum physics and the divide between the world of quantum particles and the macro universe. It is pitched in a way that I have simply never seen before. For a very narrow band of readers this book is absolutely superb. If you have been fascinated by a book on a quantum subject, like my own The God Effect on quantum entanglement, but want to dig into more depth about what is actually going on, and what was really undertaken in some of the experiments you usually have to either read a textbook or go to an academic paper. But both of these are pretty impenetrable and too maths-heavy for the general reader. Gerry and Bruno give that extra meat without requiring heavy duty mathematical support. There are equations in here, but they are used as shorthand, not to do maths. The result is quite extraordinary – it really expands on anything you can get from a popular science book without being too heavy to cope with, and for that, the authors need a huge pat on the back.
To be honest, though, I don’t think most popular science readers actually want this extra detail. On the other hand, university level physics students will find it too basic and not mathematical enough (though it could provide a good introduction before a course). This is a great book for, say, science journalists and those with a similar level of semi-professional interest – but probably not for many others.
The other slight problem is that the authors can occasionally be quite prissy and negative about guess who… science writers. Their audience in all probability. Take this quote:
Quantum theory does not predict that an object can be in two or more places at once. The false notion to the contrary often appears in the popular press, but is due to a naïve interpretation of quantum mechanics.
The problem with this attitude is that it entirely misses the point. All descriptive models of something as counter-intuitive as quantum theory are inevitably approximations – what they are really doing here is not liking someone else’s language, even though it gets the basic point across better than their version. I don’t think this is any more a problem than when physicists speak of the big bang or dark matter as if it they are facts, rather than our current best accepted theories.
There’s a similar cringe-worthy section where the authors attack the suggestion that light is a particle in the true sense, which again seems nit-picking. Their argument seems to make little sense and given Richard Feynman was happy to say ‘I want to emphasize that light does come in this form – particles’ I find their position hard to justify. So there are a couple of places where a particular slant of interpretation gets in the way of what otherwise is excellent explanation – but I think that can be forgiven.
Overall, then, a worthy and fascinating book but one that I suspect will only ever have a very limited audience.
Review first published on www.popularscience.co.uk and reproduced with permission
What we have here is an exploration of quantum physics and the divide between the world of quantum particles and the macro universe. It is pitched in a way that I have simply never seen before. For a very narrow band of readers this book is absolutely superb. If you have been fascinated by a book on a quantum subject, like my own The God Effect on quantum entanglement, but want to dig into more depth about what is actually going on, and what was really undertaken in some of the experiments you usually have to either read a textbook or go to an academic paper. But both of these are pretty impenetrable and too maths-heavy for the general reader. Gerry and Bruno give that extra meat without requiring heavy duty mathematical support. There are equations in here, but they are used as shorthand, not to do maths. The result is quite extraordinary – it really expands on anything you can get from a popular science book without being too heavy to cope with, and for that, the authors need a huge pat on the back.
To be honest, though, I don’t think most popular science readers actually want this extra detail. On the other hand, university level physics students will find it too basic and not mathematical enough (though it could provide a good introduction before a course). This is a great book for, say, science journalists and those with a similar level of semi-professional interest – but probably not for many others.
The other slight problem is that the authors can occasionally be quite prissy and negative about guess who… science writers. Their audience in all probability. Take this quote:
Quantum theory does not predict that an object can be in two or more places at once. The false notion to the contrary often appears in the popular press, but is due to a naïve interpretation of quantum mechanics.
The problem with this attitude is that it entirely misses the point. All descriptive models of something as counter-intuitive as quantum theory are inevitably approximations – what they are really doing here is not liking someone else’s language, even though it gets the basic point across better than their version. I don’t think this is any more a problem than when physicists speak of the big bang or dark matter as if it they are facts, rather than our current best accepted theories.
There’s a similar cringe-worthy section where the authors attack the suggestion that light is a particle in the true sense, which again seems nit-picking. Their argument seems to make little sense and given Richard Feynman was happy to say ‘I want to emphasize that light does come in this form – particles’ I find their position hard to justify. So there are a couple of places where a particular slant of interpretation gets in the way of what otherwise is excellent explanation – but I think that can be forgiven.
Overall, then, a worthy and fascinating book but one that I suspect will only ever have a very limited audience.
Review first published on www.popularscience.co.uk and reproduced with permission
December 25, 2017
Good and easy read for non-physicists.
Sometimes repeats itself a bit too much if you have a technical background and are already familiar with some basics of physics, but hey you learn by repetition.
Sometimes repeats itself a bit too much if you have a technical background and are already familiar with some basics of physics, but hey you learn by repetition.
March 21, 2025
The Quantum Divide refers to the gap between the quantum world and the relativistic world of Einstein as mentioned in the book as "Einstein's EPR paper" - the papers abbreviated title, which laid out is "Can Quantum-Mechanical Description of Physical Reality Be Considered Complete?" The books argument is tied directly to the Copenhagen interpretation of this paper. The concepts of entanglement and non-locality are introduced in Chapter 5. By the end, we are introduced to the Many-Worlds Interpretation (MWI) of Quantum Philosophy. The author hardly leads you astray along this lesson complete with experiments and formulas. That said, the book walks you through each one. By the end, one has a lot to chew on after learning of single photon experiments and the uncertainty of an electron pre-collapse. I had the most interesting AI conversation with my computer upon reading through chapter 5.
August 5, 2017
Relatively technical overview of QM
The Quantum Divide attempts to bridge the gap between pop sci books on QM and deeply mathematical textbooks that require formal study to understand. QM is introduced and explained by describing a handful of experiments that exhibit Quantum effects, with little of the history and biography that most authors fall back on in lieu of being able to explain the actual science without going into the maths. As such, it is quite refreshing, but it doesn't really provide a deeper understanding of the subject. Some equations are presented, but no calculations are shown so it really only serves to introduce the notation physicists use. This might be useful as a bridge to further, deeper study, but in itself it is just a rather dry way of describing the subject.
The Quantum Divide attempts to bridge the gap between pop sci books on QM and deeply mathematical textbooks that require formal study to understand. QM is introduced and explained by describing a handful of experiments that exhibit Quantum effects, with little of the history and biography that most authors fall back on in lieu of being able to explain the actual science without going into the maths. As such, it is quite refreshing, but it doesn't really provide a deeper understanding of the subject. Some equations are presented, but no calculations are shown so it really only serves to introduce the notation physicists use. This might be useful as a bridge to further, deeper study, but in itself it is just a rather dry way of describing the subject.
January 28, 2018
A relatively easy and entertaining introduction to the quantum world. I picked this up on a whim from my local library and was surprised to find that the writing is clear, logical and pleasing to read. I think this book is most suitable to those with a little background (high school maths and physics) and have an interest in quantum physics. Using experiments and good diagrams to highlight the key theories in quantum physics, it enforces the general consensus that the quantum world is indeed weird and much of it remains a mystery.
December 28, 2018
3.5 -- While at the edge of my mathematics/physics capabilities, this book did a good job explaining some typical quantum experiments to laymen. I had always wanted real-life examples of the experiments used to demonstrate wave/particle duality and entanglement, and this series of articles hit the mark. By the last few chapters my ability to understand the concepts was dwindling, but I probably wouldn't have enjoyed the book as much if it felt oversimplified or condensed.
November 22, 2020
Amazing book for any one with semi professional interest in Quantum Mechanics. The book successfully presents the quantum world in a way that enables a physics enthusiast to delve a bit deeper into the quantum without the heavy math.
September 13, 2019
The book can be summarized as having two sections. One deals with experiments conducted to study the probabilistic nature of the world and the other about serious philosophical discussions on different interpretations of those experiments.
Aptly titled quantum divide talks about the boundary that divides the quantum and classical world.
Although the book is a hard read, I'm willing to revisit this book in the future.
Regards,
Vinay
Aptly titled quantum divide talks about the boundary that divides the quantum and classical world.
Although the book is a hard read, I'm willing to revisit this book in the future.
Regards,
Vinay
Displaying 1 - 9 of 9 reviews