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| View Larger Image | A Shortcut Through Time: The Path to the Quantum Computer
by George Johnson
| | List Price: | $14.00 | | Price: | $11.90 | | You Save: | $2.10 (15%) |  | | Available: | Usually ships in 24 hours | | | | | Sales Rank: | 433164 | | Studio: | Vintage | | | Binding: | Paperback | | Number Of Pages: | 224 | | Publication Date: | February 10, 2004 | | Publisher: | Vintage |
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EDITORIAL REVIEWS |
Product Description
In this remarkably illustrative and thoroughly accessible look at one of the most intriguing frontiers in science and computers, award-winning New York Times writer George Johnson reveals the fascinating world of quantum computing—the holy grail of super computers where the computing power of single atoms is harnassed to create machines capable of almost unimaginable calculations in the blink of an eye.
As computer chips continue to shrink in size, scientists anticipate the end of the road: A computer in which each switch is comprised of a single atom. Such a device would operate under a different set of physical laws: The laws of quantum mechanics. Johnson gently leads the curious outsider through the surprisingly simple ideas needed to understand this dream, discussing the current state of the revolution, and ultimately assessing the awesome power these machines could have to change our world. |
CUSTOMER REVIEWS (Average Customer Rating: 4.5 based on 17 reviews)
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Dead and Alive: Schrödingers Cat Revealed 
George Hohnson's little book, "A Shortcut in Time," reveals the truth of Schrödinger's Cat, which, as a quantum event was both dead and alive-until its state was acutally observed. He makes it possible to grasp the meaning of quantum states as arrays of possibility, and no more than possibility until made into concrete events in space and time. Johnson gives clarity and meaning to the word "superposition." If the reader wishes to get some feel for the nature of the principle of uncertainty, look here. This book makes explicit what Einstein meant when he referred to "spooky action at a distance," or "God does not play dice with the universe."
His discussion and explanation of possible quantum computers from some future date make the obscure, difficult subject something real for the non-mathematics speaker. If one get's the Disneyland Jungle Cruise joke about seeing "the back of water," then get this book. It is the view from inside the looking glass at the quantum world.
Johnson presents mathematical proofs and demonstrations of deep quantum concepts, but he uses arithmatic. It gets as clear as 1+1=2 and 1-1=0.
August 10, 2008 | |
Interesting Introduction to Quantum Computing
"A Shortcut Through Time" is a well-written introduction to the complex topic of quantum computing. Quantum computing, in a general sense, is the utilization of various quantum mechanical phenomenon, such as entanglement, for the benefit of a powerful computer, or data processing engine.
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.
November 06, 2007 | |
NP=P
The hardest problem is revealing how protein folding occurs. "Some of the amino acid beads are `hydrophobic' or water-fearing, avoiding the cellular fluids by congregating inside the cell. Others are hydrophilic, migrating to the outer edge of the protein." There is a 3D tug-of-war to find the path that leads to the correct form. Searching though the labyrinth of possible foldings suffers from exponential explosion.
1. Quantum Computers could be used to simulation simplified proteins. The Quantum machine may be able to predict how the protein would fold.
2. The traveling saleman problem is a Non-Determinist Polynomial problem require exponential amounts of time that too solve. Conventional computers for 10 cities would require exploring 10X9X8X7X6
X5X4X3X2X1 = 3,628,800 trajectories with 1,814,400 unique trajectories.
3. "Satisfiability Problem", the classic problem is planning a party. A will only attend if C does and E doesn't, while C requires that B and G be there. 10 invitations will have 2^10 combinations to explore. 40 invitations results in a trillion combinations.
4. Shors algorithm of calculating large number factors offers hope that an quantum computer would be able to crack the domain of NP complete. In Shor's algorithm a number wave can be formed. Factors for 15, find a seed value 7 by random selection, raise 7 by I and mod by 15 resulting in the series: 1,7,4,13, 1, divide the period of the wave in half, at 4 and divide by 2 and then apply as a power to 7, 7^2 yielding 49, pick two integers to the left and right, 48 and 50 and mod by 15, resulting in the factors 3 and 5. With large and longer numbers, the rapidly increasing load of calculations is overbearing. A load that only a quantum computer could handle.
5. A fourier transform could run on a quantum computer. Fourier transform involves generating a bunch of test waves, each with a different period, and trying them to see if they match the wave you want to analyze.
6. "Unlike the head of the Turning machine, the laser in the quantum cellular automation doesn't read the information on the tape. It fires off order to be carried out, simple rules. The qubits essentially read each other (entanglement)." The atoms don't need to adjacent, atom a might be entangled with atom D, or E with B. In quantum CA, the rules are internal, consequences of the ways the qubits interact." The result is the quantum equivalent of AND, OR, and NOT gates. Given a problem to solve, coded as an initial pattern of qubits, and the proper program of laser pulses, the system will evolve to produce the answer, in happy isolation from the outside world."
7. Grover's algorithm can be used to perform a quantum search for data. Suppose names with a binary rank, Gina 00001 through Lolly 10000 (16 names, 16 binary ranks). Using 5 qubits all the ranks can be represented simultaneously. Suppose your searching for Grover 01001. Find by subtracting 01001 from the names. When it found the right match, it would amplify its wavelet, and juxtapose the others, peak to trough, canceled each other out. "The quantum computer examines the entries simultaneously and picks out the ciphertext we are seeking, which is linked to the key that produced it. Step by step, this wavelet's amplitude is inflated while the others are squeezed down."
May 31, 2007 | |
simple metaphors 
Johnson tackles a difficult subject. One that is very non-intuitive to a reader unversed in physics. Yet in simple but clear metaphors, he seems to succeed.
He shows the difference between a Turing machine implemented via classical physics and a hypothetical quantum computer. The idea of a parallel computation acting on a superposition of states is shown not to be too awkward to grasp. This is enhanced by a discussion of Shor's algorithm and why factorising large numbers is vital to code breaking.
January 18, 2006 | |
Hoping for more... 
Even though Richard Feynman once quipped, "...nobody understands quantum mechanics," I was still hoping to come away with a better understanding of quantum computing than Johnson provides. The author spends too much time covering the general principles of computing and not enough time on quantum computing. Specifically, he beats the reader over the head with the rather clear concept of the Turing machine. He forays into the tinkertoy computer -- an interesting historical curiosity, to be sure -- but does not make clear how the tinkertoy computer relates to quantum computing, other than that it is an example of a Turing machine, and does not even explain the tinkertoy machine well enough to get a clear idea of its functioning. Much the same is true for the simple Geniac switch, love of his childhood, which occupies an unseemly number of pages. At the same time, quantum computing is not covered precisely enough for the reader to digest and express the gist of it.
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.
January 02, 2006 | |
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