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A Shortcut Through Time: The Path to the Quantum Computer Paperback – February 10, 2004
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From Publishers Weekly
Johnson has been nominated for several awards for earlier books on physics and physicists (Strange Beauty; Fire in the Mind). Here he sticks mainly to science, providing a quick overview of a cutting-edge union between quantum theory and computing. The book begins by describing a computer as "just a box with a bunch of switches." Although today's computer switches are imbedded in circuitry, they can in principle be made of any material, like the early banks of vacuum tubes; Johnson also recalls a tic-tac-toe-playing machine created from Tinkertoys in the 1970s. An ordinary computer switch, binary in nature, registers as either a zero or a one, but if a single atom were harnessed as a switch, its dual nature as both particle and wave means it could be "superpositioned," simultaneously zero and one. A series of such switches could handle complex calculations much more swiftly than conventional computers: an entertaining theory, but impractical. Except that a quantum computer's ability to factor large numbers-determining the smaller numbers by which they are divisible-would have a critical application in cryptography, with a string of atoms used to create (or break) complex codes. After discussing competing projects that aim to make the theory of quantum computing a reality, the book concludes with ruminations on the implications of the projects' possible success. Using "a series of increasingly better cartoons" and plain language, Johnson's slim volume is so straightforward that readers without a technical background will have no problem following his chain of thought. Illus.
Copyright 2003 Reed Business Information, Inc. --This text refers to an out of print or unavailable edition of this title.
From Library Journal
It's hard to imagine how the newest Pentium chip could pack 40 million electronic switches into a nickel-sized bit of silicon and even harder to imagine what that means for computing. A recipient of the Science Journalism Award, Johnson should make it all clear.
Copyright 2002 Reed Business Information, Inc. --This text refers to an out of print or unavailable edition of this title.
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What is interesting to the computer programmer is a) how the program is loaded, b) how processing is accomplished, and c) how the output is read. We can set an initial state by shining a laser on a bunch of particles (Johnson pretty much leaves it at that). The problem here is that setting the initial state of a program is not the same as loading the program itself, in other words, somewhere there must be a distinction between loading code and loading data, as well as code operating on data. It seemed to me that Johnson skirts the issue by ignoring this distinction and leaving the processing "black-box" to the collapse of probability waves of entangled particles whose initial state was set by a laser. The probability waves' collapse -- by what mechanism we never find out -- is somehow controlled by a poorly explained mathematical theory that normally governs the behavior of cellular automata. On the other hand, if code and data are one and the same, then it seems at first blush that the output should deterministically be known at the start, or that the output would be no more helpful than the input.
My feeling persists, however unfair, that science writing should be left to the rare scientists in each field who possess the pedagogic and literary skill to explain their work to a lay audience, and not left to science journalists. Throughout the text, I kept waiting for that spark that synthesizes the concepts into some feeling of real comprehension, but never got it. Perhaps, given Feynman's assessment of quantum mechanics, that elusive spark is impossible -- especially for a popular science book. On the other hand, maybe it is and "A Shortcut Through Time" isn't it.
(Problems that scale exponentially in the classical domain can scale linearly in the quantum world.)
Even more amazing, all this is accessible for a non-technical audience, with analogies, examples and illustrations.
If you've ever wondered what all the hoopla is about, read this and find out.
In a more basic sense, this is a book about the potential for computing devices that operate at the atomic level. This engaging and well-written book is, in various parts, a historical overview of computing, a vivid description of quantum mechanics and an exposition of the potential for quantum computing.
While written for a general audience, several advanced topics are covered in a unique manner, such as a good description of "NP-complete" (Nodeterministic Polynomial-time) problems.
Highly recommended for those with an interest in learning more about the potential for a new approach to computing.