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1 of 1 people found the following review helpful
4.0 out of 5 stars Fantastic incite into the applications of quantum effects
George Johnson presents the first book i have read that talks about the application of quantum effects, the majority of books and lectures on quantum physics discuss only the effects we observe or think we observe. He presents a clear view of the quamtum world and explains quantum superposition and quantum applications like that of Feynman. I will stress that it is not...
Published on 26 April 2003 by Frank

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1 of 2 people found the following review helpful
3.0 out of 5 stars Beginners Book
I am a computer science student and bought byself (next to some technical references - Nielsen & Chuang) this book and "The quest for the quantum computer". I started reading the later which I found an excellent book giving a thourough historical, conceptual overview of the field. After that I read Johnson's book which I found very very meager compared to the first I...
Published on 4 Nov 2003 by Jurgen Van Gael


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1 of 1 people found the following review helpful
4.0 out of 5 stars Fantastic incite into the applications of quantum effects, 26 April 2003
By 
Frank (Much Hadham, Herts United Kingdom) - See all my reviews
George Johnson presents the first book i have read that talks about the application of quantum effects, the majority of books and lectures on quantum physics discuss only the effects we observe or think we observe. He presents a clear view of the quamtum world and explains quantum superposition and quantum applications like that of Feynman. I will stress that it is not required to know about quantum physics to read this book, it will be clear to everyone what he is talking about and is illustrated by clear diagrams. He explains how quantum computers can use superposition to factorise large numbers in pico seconds making RSA encryption obsolete, a method of quantum encryption and the problems faced by todays physicists measuring particles that can exist in two places at once, whilst at the same time exist in none. A fantastic read for Physics students worldwide.
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5.0 out of 5 stars Simply Enthralling, 8 Dec 2007
By 
P. Froggatt (UK) - See all my reviews
(REAL NAME)   
In "A Shortcut through Time" George Johnson has successfully encapsulated the flavour of one of the most contemporary sciences of our modern world. Due to the nature in which the mind works many will find the concepts in this book hard to swallow; but that does not mean we should not try and digest them. For it is only by applying ourselves do we progress.

Many will read this book and claim to understand, but will simple only have a rudimentary feel for the field, for its complexity and innovative methodology is known only to a select few. It deals with the subject, as the subtitle suggests of quantum physics; a basic principle of which is the ability for `something' to be in two places at the same time, then snap instantaneously (i.e. does not transverse any midsection) into one of four different positions - {1}, {0}, {1, 0} and {null} in stark contrast to modern Turing Machines which operate on a simple {1}, {0} system.

George Johnson will provide you, as the reader, with a window to gaze at the pinnacle of modern human science; an opportunity which should by no means missed. "A Shortcut through Time" is elegantly written with a fluid and charismatic feel, delightfully illustrated throughout, and as a follower of popular science I can recommend this book to anyone.
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4.0 out of 5 stars Good read about an exciting possibility, 27 Aug 2003
By 
Dennis Littrell (SoCal/NorCal/Maui) - See all my reviews
(TOP 500 REVIEWER)   
One of science writer George Johnson's aims in this book is to explain to a general readership how quantum computers might work. The key word is "might." As it stands now there are no quantum computers at work; and, although there is apparently no theoretically reason they won't be developed in the future, there are a host of practical problems to be solved that suggest they may never be developed.
Johnson acknowledges as much when he quotes French physicists Serge Haroche and Jean-Michel Raimond as saying that the small scale "hands-on experiments" with a few qubits that are currently being done "are more likely to teach us about the processes that would ultimately make the undertaking fail" than to teach "us how to build a large quantum computer." (p. 169)
As I understand it, basically the idea behind quantum compters is that (somehow) individual quanta (atoms, photons, electrons) are able to be in a particular state or not to be in a particular state; that is, either the equivalent of yes or no, but also in an indeterminate state; that is, a state that would signal yes and no at the same time! Somehow (and I hope I am forgiven for not fully appreciating this)--somehow because of this fabled indeterminancy, quanta can be used to compute at a speed that is more than exponentially faster than digital computers.
Johnson spends some series ink in trying to show how the atoms can hold and crunch numbers as long as they are not disturbed; that is, not measured in any way (which would bring about the famous "collapse of the wave function"). In this manner a problem that would take a digital computer weeks or months to solve could be solved in a fraction of a second. Problems now actually impossible to solve in any reasonable length of time might become tractable after all. The traveling salesman problem which grows exponentially more complex with the addition of each city, might very well yield to a quantum computer since the computational ability of a quantum computer itself grows exponentially with the addition of more quanta.
Wow. One of the reasons there is real money going into trying to develop these seemingly magical machines is that at present all the cryptography used by the military and big corporations relies on the fact that digital machines, no matter how fast, are not able to factor the codes. However, a quantum computer could. Furthermore, as Johnson explains, a quantum computer could also develop cryptography that could not be decoded. So, whoever gets there first--assuming somebody can--will at the very least make a whole lot of money.
What I found more interesting than the hope for a quantum computer are some of the insights into the quantum word that Johnson provides incidentally. The biggest stunner for me was his assertion that quantum events can be used to generate random numbers. It may come as a surprise to many people but in the world of classical mechanics there is literally no such thing as a truly random number generator. But because radioactive nuclei decay on a random basis, they can, according to Johnson, be used to generate random numbers. He writes that numbers generated in such a manner are "undeniable random." (p. 91)
Apparently this conclusion is a consequence of quantum indeterminacy. In a way, it is a circular conclusion since if we could somehow predict the rate of radioactive decay we would violate indeterminacy. I say "circular" when perhaps I should say "as a matter of faith" because there is no way a stream of numbers derived from radioactive nuclei decay can be proven to be random. Indeed, no string of numbers can, by examination, be proven to be random. If QM is true--and it is massively established--then the numbers are random.
Perhaps this idea of randomness is similar to the notion of "nothing" in that it is only defined in a negative way, by which I mean random is the absence of order, and order is in the eye of the beholder. What seems random to human beings may be quite orderly from another point of view.
Some of the book is pure fantasy. His discussion of quantum banknotes in Chapter 9 is an example of something that is useful to think about because of the light it sheds on the nature of the quantum world, but any chance that we would actually use quantum banknotes (requiring temperatures near absolute zero!) approaches the null set. (p. 146)
Other parts of the book are largely tangential (but interesting nonetheless). For example Johnson's exploration in Chapter10 of "nondeterministic polynomial-time" problems, such as the above mentioned traveling salesman problem, the protein-folding problem and the software verification problem, is very interesting. I was not aware that such problems were linked, but according to Johnson if one is solved, the others would yield as well. The current thinking is that the only hope of solving such intractable problems is a large-scale quantum computer. (p. 164)
Johnson is hopeful that such a computer can be developed and bases his hope in part on recalling just how intractable the problems toward the development of the sort of computers we have today seemed in the 1940s in the days of the vacuum-tubed Eniac computer which filled an entire room and had only a small fraction of the computational ability of my desktop. (p. 140) However, whether history will repeat itself and the impediments be overcome remains to be seen. It's exciting to think that they will.
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5.0 out of 5 stars From a New York Times science writer., 10 April 2003
By 
Palle E T Jorgensen "Palle Jorgensen" (Iowa City, Iowa United States) - See all my reviews
(REAL NAME)   
This is an author who has the ability to make otherwise
intimidating subjects seem like child's play. It is for readers who occasionally stop and wonder about what one term or the
other in the New York Times Science Section really means, or at least want to know a little more;---terms like quantum, Turing mashine, Shor's algorithm, quantum secrecy. The material is presented in a clear and systematic way, and yet in a fast moving style. Not many authors have both George Johnson's knowledge of science and his ability to communicate it in a delightful presentation; --and addressed to everyone. Another one who comes to mind is the late George Gamow. His whimsy books have offered both depth, and fun for generations of readers. They still get reprinted now fifty years, or so, after their first editions.
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5.0 out of 5 stars An invitation., 4 April 2003
By 
Palle E T Jorgensen "Palle Jorgensen" (Iowa City, Iowa United States) - See all my reviews
(REAL NAME)   
This is an author who has the ability to make otherwise
intimidating subjects seem like child's play. It is for readers who occasionally stop and wonder about what one term or the
other in the New York Times Science Section really means, or at least want to know a little more;---terms like quantum, Turing mashine, Shor's algorithm, quantum secrecy. The subject is interdisciplinary, involving ideas from quantum theory, math, and computer science. But the presentation is inviting, and should be both accessible and engaging for everyone, even readers with no science background knowledge. Not many authors have both George Johnson's knowledge of science and his ability to communicate it in a delightful presentation; --and addressed to everyone. An intellectual treat! Another series of popular science books that comes to mind is that of the late George Gamow. His whimsy books have offered both depth, and fun for
generations of readers. They still get reprinted now fifty years, or so, after their first editions.
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1 of 2 people found the following review helpful
3.0 out of 5 stars Beginners Book, 4 Nov 2003
By 
Jurgen Van Gael (Cambridge, UK) - See all my reviews
(VINE VOICE)    (REAL NAME)   
I am a computer science student and bought byself (next to some technical references - Nielsen & Chuang) this book and "The quest for the quantum computer". I started reading the later which I found an excellent book giving a thourough historical, conceptual overview of the field. After that I read Johnson's book which I found very very meager compared to the first I read.
Johnson's book is for the abolute beginner and gives only very limited insight in the current state of the field. I would recommend this book to someone without an education in physics/mcomputer science/mathematics. For people who know a little (from popular science books) quantum mechanics and computer science, this book will give you no more information than you will get on online encyclopedia.
If you are interested in Quantum Computing and you are not an absolute beginner, start with Brown's "The quest for the quantum computer".
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