A book about a simple experiment

Promotional image from Dutton, composited by Chad Orzel

I got a pre-release of Anil Ananthaswamy’s upcoming book Pass through two doors at the same time Some time ago, when I was busy with my book, I couldn’t read it in time to promote it, but I did manage to finish it before it was released, so you got this review ahead of time.

This is a 250+ page book on the double slit experiment. Your initial reaction to the concept might be a lot like Kate’s: “Is this really enough to support a whole book?” However, this isn’t just any experiment — it’s Feynman’s famous experiment that embodies the quantum mechanics of quantum mechanics. “Core Mystery”. Or, as the subtitle puts it, “an elegant experiment in capturing the mysteries of our quantum reality.” All the weirdness of quantum mechanics can be explained by the double slit experiment.

To be fair, though, Ananthaswamy does cheat by including many variants in the base scheme. He also made the perfectly reasonable decision to re-solve the problem with a Mach-Zehnder interferometer instead of a pair of slits, as this would give a much cleaner set of binary results – a particle comes in and you’ll Get a single particle output from one of the two output ports. This avoids a lot of the complexity involved in determining the spatial distribution of particles in a true double-slit mode, but still has all the basic physics: if anything you send into the input behaves like a classical particle, then you have 50 /50 chance to see it coming out of either output port. On the other hand, if it behaves like a wave, you end up with 100% of the input going out through a single output. This allows for simple and unambiguous testing of various quantum phenomena and explanations.

Of course, from a mathematical point of view, this experiment is very simple: you calculate a probability distribution that you expect to see in the output, repeat the experiment many times, and that’s it.The core and mysterious part of the question is to ask “what real “Happening” between the source and the detector — that is, how you interpret quantum predictions. So Ananthaswamy mainly uses the “double slit” as a means of exploring various possible explanations for quantum physics, in the same way that Adam Becker’s book in my last set of book reviews does. Along the way, he came across a lot of good stuff – obviously Copenhagen and the many-worlds discussion, but also a nice and detailed discussion of Bohemian mechanics and several different variants of spontaneous collapse theory, and even a A section is devoted to the cognitive novice, “Quantum Bayesianism” (often abbreviated to “QBism”).

like Ananthaswamy before the edge of physics It’s also a bit like a travelogue (though not as exciting). Ananthaswamy explores variations on the double-slit formulation by interviewing a number of physicists, from theorists like Sean Carroll (here, many-worlds proponents) with high-level views on the explanation, to experimentalists like Markus Arndt and Aephraim Steinberg Responsible for operating labs for real-world testing. This offers some different perspectives and makes the book feel less narrowly focused on a single experiment than would suggest. Ananthaswamy’s own voice is not too intrusive, resulting in a very balanced treatment of all the various interpretations considered: each is described by its own proponents, with minimal editorial.

The double-slit analogy feels a bit far-fetched in one or two places—for example, the relevance of Bell’s theorem takes a while to become clear. There are also some missed opportunities – it would be interesting to see, for example, some discussion of the Hong-Ou-Mandel experiment that demonstrated the interference of photons from two different sources. These are nitpicks, though – overall, this is an excellent and comprehensive exploration of the famous double slit experiment, and a great demonstration of Feynman’s famous thesis that this surprisingly simple The experiment is the perfect encapsulation of all the mysteries of quantum physics.

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