One of the most readable books I've ever read. Extra credit to Seth Lloyd for making a mind-blowing topic such as Quantum Computation easier to grasp. ( )

Although this book was written by one of the leading researchers in the field, it pretty much covers the same ground as Charles Seife's Decoding the Universe. Unfortunately, it does so with considerably less elegance and clarity. ( )

I could only bear two or three chapters of this book, so this quasi-review might not be entirely fair.

The idea of a quantum computer was first broached by Richard Feynman and others in the 1980s. Lloyd gives us four reasons why building them is important:

* "The first is that we can ... We now possess lasers stable enough, fabrication techniques accurate enough, and electronics fast enough to perform computation at the atomic scale."
* "The second reason is that we have to -- at least if we want to keep building ever faster and more powerful computers." (This is followed by the customary, breathless retelling of Moore's law.)
* "The third reason to build quantum computers is that they allow us to understand the way in which the universe registers and processes information."
* "The final reason to build quantum computers is that it's fun."

Reasons one, two, and four are inane and unlikely to impress anyone but the most simple readers looking to be dazzled by science candy. His prose elsewhere is vapid and patronizing (which is why I put the book aside):

'I began the initial meeting of my MIT graduate course on information in the manner I begin all of my courses: "First," I said to the twenty-odd students, "you ask questions and I'll try to answer them. Second, if you don't ask questions, I'll ask questions. Third, if you don't answer my questions, I'll tell you something I think you ought to know. Any questions?"'

'I waited. No response.

'Something was wrong. Normally, MIT students are more than happy to try to stump the professor, particularly if the alternative is that the professor will try to stump them.'

I have a question: "How do I drop this course right now, you pompous fool?"

Lloyd's third reason gets to the thesis of his book: that the universe is a quantum computer. What is it computing? It's computing itself. Why? Well, because he says it is.

What Lloyd and others have shown is that they can model physical processes using information-processing metaphors. That's all well and good, but you can't leap from this metaphor to reality, as Lloyd does in this book. He wants us to believe that the universe really is a computer simply because it seems like one when you consider it that way. This is such a fundamental flaw in logic that I'm amazed this book got published.

I am probably being a bit harsh, but this book has gotten plenty of gushing reviews -- I think it can stand some harshness. I'm genuinely interested in learning the theory behind quantum computers, but I could do without all the grandiose, unsupported claims about life and the universe.

(Reviewed at Question Technology: http://www.questiontechnology.org/blo...) ( )

Best current book on multiverse as a quantum computer (July 2007). ( )

Gives primacy to information theory, saying that the universe is one big quantum computer. Lloyd states some of his points on www.edge.org (under the heading "quantum monkeys").

Strangely lacking in argument, PtU contains a remedial-level overview of classical information theory, theory of computation and their quantum counterparts. It reads like an updated Pythagorean mysticism, or, less sympathetically, an orgy of computational fetishism. Lloyd is undeniably clever and convivial, but he has yet to make his case for universal computationalism. ( )