Decoding Reality: The Universe as Quantum Information. By Vlatko Vedral. Oxford University Press; 256 pages; $29.95 and £16.99. Buy from Amazon.com, Amazon.co.uk

ONE of the most elusive goals in modern physics has turned out to be the creation of a grand unified theory combining general relativity and quantum mechanics, the two pillars of 20th-century physics. General relativity deals with gravity and time and space; quantum mechanics with the microscopic workings of matter. Both are incredibly successful in their own domains, but they are inconsistent with one another.

For decades physicists have tried to put the two together. At the heart of the quest lies the question, of what is the universe made? Is it atoms of matter, as most people learned in school? Or some sort of energy? String theory, currently a popular idea, holds that the universe is made up of tiny vibrating strings. Other equally esoteric candidates abound. Indeed, cynics claim that there are as many grand unified theories as there are theoretical physicists attempting unification.

Now Vlatko Vedral, an Oxford physicist, examines the claim that bits of information are the universe's basic units, and the universe as a whole is a giant quantum computer. He argues that all of reality can be explained if readers accept that information is at the root of everything.

So what is information? Mr Vedral's notion of information is not the somewhat fuzzy concept most people have of it, but a precise mathematical definition that owes itself to Claude Shannon, an American mathematician considered to be the father of “information theory”. Shannon worked at Bell Labs, at the time the research arm of AT&T, a telephone giant, and in the 1940s became interested in how much information could be sent over a noisy telephone connection. This led him to calculate that the information content of any event was proportional to the logarithm of its inverse probability of occurrence. (Unlike many popular-science books that eschew equations, Mr Vedral includes a couple and tries his best to explain them to the reader.) What does the equation mean? As Mr Vedral points out, it says that an unexpected, infrequent event contains much more information than a more regular happening.

Once he has defined information, Mr Vedral proceeds to show how information theory can be applied to biology, physics, economics, sociology and philosophy. These are the most interesting parts of the book. Of particular note is the chapter on placing bets. Mr Vedral gives a good description of how Shannon's information theory can be applied to winning at blackjack or in buying shares (Shannon and his friends made fortunes in Las Vegas as well as on the stockmarket). And his exposition of climate change and how to outwit the CIA make entertaining reading. One quibble: Mr Vedral often digresses from the point at hand, so the overall effect tends to be a bit meandering.

Mr Vedral's professional interests lie in quantum computing and quantum information science, which use the laws of quantum mechanics respectively to build powerful computers and render codes unbreakable. There is a lot of discussion of both, which is very welcome because there are not many popular science books that cover these relatively young fields. Quantum computers, as Mr Vedral points out, “are not a distant dream”. Though still rudimentary, “they can solve some important problems for us that conventional computers cannot.”

Unusually for a physicist, Mr Vedral spends a fair bit of time talking about religious views, such as how God created the universe. He asks whether something can come out of nothing. Throughout the ages philosophers and theologians have debated this question with respect to Judeo-Christian faiths, in which dogma holds that the world was created from the void, creation ex nihilo. Others side with King Lear who tells Cordelia that “Nothing can come of nothing.” Mr Vedral makes a persuasive argument for a third option: information can be created out of nothing.