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The Demon and the Quantum – Robert J. Scully and Marlan O. Scully ***

It’s one of the inherent oddities of quantum theory that a quantum particle can be in more than one state at once – and for me, this must be a quantum book, because it manages to be both excellent and not-so-good at the same time.
Let’s start with the excellent. Robert Scully, with help from his physicist father Marlan, weaves a fascinating fabric of ideas from ancient Greece and quantum physics to provide an introduction to an exploration of the overlaps between thermodynamics and quantum theory. This leads on to the description of the concept of a ‘quantum eraser’ that may (there’s some dispute among physicists) be a demonstration of the ultimate quantum strangeness – that you can change the outcome of a quantum effect after it has, in effect, already been committed.
Scully starts in a gentle fashion and provides a solid introduction to thermodynamics, a subject that has rarely been given an effective popular science treatment. By using the clever conceit of a heat engine powered by a single molecule, he enables the reader to get a good grasp of engine efficiency from a modern viewpoint, encapsulating the wisdom of the steam age, but bringing it into a modern context.
So far, so good. However, the more than half of the book that is primarily about quantum phenomena has real problems. One is a tentative introduction of God into the equation. I don’t know if Robert Scully is explicitly saying that God is a necessary part of his thesis – it’s never stated quite that strongly – but the subject is touched upon several times without making it clear what his (Scully’s, not God’s) intentions are. This could be lived with. But the problem that brings the rating of this book down to three stars is that the quantum chapters aren’t well enough explained for a general reader.
There are too many assumptions about what people know, and the description of both the single atom quantum heat engine and the quantum eraser are likely to be baffling to anyone without a degree in physics. There are also big gaps in what’s presented. There’s a section that claims that the concept of the quantum eraser takes away the paradoxical nature of the EPR paradox that first introduced the concept of quantum entanglement. I was excited by this, having written a book about entanglement, but despite that background I couldn’t understand what it was saying about EPR, or how what was said took away the paradox. It’s frustrating, because the intention here is excellent, but the science writing isn’t at a level that will work for a reader of popular science.
I would highly recommend this for physics and engineering undergrads and above, however. There are some excellent challenges to aspects of physics you are likely to get in your course – and good insights into the way a real scientific theory is developed from the description of the discussions between different groups over the quantum eraser. But, sadly, I can’t recommend it for anyone else.
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Review by Brian Clegg

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