Quantum 2.0 - Paul Davies ****

Unlike the general theory of relativity or cosmology, quantum physics is an aspect of physics that has had a huge impact on everyday lives, particularly through the deployment of electronics, but also, for example, where superconductivity has led to practical applications. But when Paul Davies is talking about version 2.0, he is specifically describing quantum information, where quantum particles and systems are used in information technology. This obviously includes quantum computers, but Davies also brings in, for example, the potential for quantum AI technology.

Quantum computers have been discussed for decades - algorithms had already been written for them as early as the 1990s - but it's only now that they are starting to become usable devices, not at the personal level but in servers. In his usual approachable style, Davies gives us four chapters bringing us up to speed on quantum basics, but then brings in quantum computing. After this we don't get solid quantum information theory, but a mix of this and the more exotic aspects of quantum physics from teleportation, through quantum biology and vacuum energy to black holes and time travel.

It's all good fun and informative if you haven't read about quantum theory before, though much of this extra material has been well covered elsewhere - I would have preferred a book focussed solely on quantum information theory and its implications (including, of course, that quantum AI). Davies is definitely an enthusiastic tour guide on this trip around the quantum.

Unfortunately, that enthusiasm has something of a downside. There are plenty of limitations to quantum computers. Not only are they tricky to keep going, and to get information usefully in and out of, they are not general purpose - quantum computing algorithms are limited. This doesn't always come across, for example in the suggestion of using them in climate modelling. Scientific claims in the early stages of technology transfer need to be strongly monitored for the tendency of university press offices (and researchers eager for funding) to over-promise and under-deliver. There is no sense of testing viability here. Similarly, when describing a fairly unlikely means of detecting dark matter's presence using quantum technology, Davies gives us no clue that there is a strong alternative theory that dark matter particles don't even exist. The particle theory is stated as if fact.

Increasingly popular science goes beyond the 'gee-wow, this is what we know' to give a clearer picture of the gaps in our knowledge. And this could have been done better. But this doesn't make it a bad book - and Davies does a great job on the quantum basics and the theory behind quantum computing.

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Review by Brian Clegg - See all Brian's online articles or subscribe to a weekly email free here