A Shortcut Through Time : The Path to the Quantum Computer

Rating:
Summary: Tidy Bit Of Science Writing
Review: * George Johnson's A SHORTCUT THROUGH TIME could be subtitled
"A Beginner's Guide To Quantum Computing & Cryptography", with
this book exploring the bizarre quantum phenomena that could,
in potential, be used to perform computations on a range of
numbers simultaneously, or produce ciphers that are literally
impossible to crack by analytical means.

Trying to say more about the concepts discussed in this book
in a short review is impossible -- explaining how a particle
will simultaneously exist in all its possible states at once
until it's measured will give either a blank stare or a bland
"yeah right I know", meaning it didn't really register -- but
it isn't necessary, because Mr. Johnson does a right nice job
of explaining such matters in this neat brief book.

His writing is extremely clear and concise, at least relative
to the difficult matters he is discussing, and the book is
tidily illustrated. This is, to be sure, a book for beginners,
and in fact it spends some time up-front explaining basics
of computers before it moves on to quantum effects. A
specialist will likely have NO use for it, and might even be
a bit scornful at Mr. Johnson's occasional excursions into
arm-waving.

In fact, I did have some real problems with his discussions
of Shor's and Grove's quantum-computing algorithms, when
Mr. Johnson did seem to be getting into some real arm-waving.
Well, given the difficulty of the material, he was likely to
fall into that trap in places, and maybe I should just give
him the benefit of doubt, read that material again a few times,
and sleep on it.

However, I was basically familiar with quantum computing and
cryptography (at a layman level) before I read this book, and
at the outset thought it might not tell me anything I didn't
already know. I was wrong since I got a tidy explanation of
the application of quantum teleportation to cryptography
(blank stare out there?), and some other nice tidbits.

Besides, I was thoroughly impressed by Mr. Johnson's
sensibility in his comments about technical writing and his
degree of cautious skepticism in dealing with physicists, some
of whom seem to be slightly around the bend. The late Dick
Feynman, who plays a part of sorts in this book, could
actually understand what the such sorts were saying and
nail them, but the rest of us will just have to sympathize
with Mr. Johnson when he makes comments such as:

"Gilles Brassard tells me that each dim flash, on the average,
contains perhaps one-tenth of a photon, an idea I find rather
difficult to grasp."

You just gotta like this guy.

Rating:
Summary: Like a video game walk through for applied quantum theory!
Review: Most "beginner" books on quantum theory I've tried to read take the reader on a chronological tour of who discovered or developed what. I hate that. Just becase B happened before A doesn't mean that it's easiest to understand if you describe B before A!

Well, Johnson doesn't cheat the reader by taking this easy way out. He's distilled all the background necessary to understand the key concepts behind quantum theory and how it can be used in a crazy revolutionary way to compute, boiled it down to the bare minimum required and organized it in such a way as to make things crystal clear.

No oblique anecdotes. No historical "human-interest" segues dumped in for filler. Just applied quantum theory 101, pure and simple.

Reading this very compact book took me all of half a day and after that I felt like I had just climbed a set of stairs from darkness to illumination. Before: "What's quantum theory?" After: "I get it now."

There is some sensationalism, but it's easy to read around that. Besides, hype is engaging! It makes you go "Wow, cool!"

Rating:
Summary: Good read about an exciting possibility
Review: 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.

Rating:
Summary: Brain Freeze
Review: This book is well written, clear, and concise. It is also challenging, amazing, and, at times, difficult to understand. Johnson begins with some brain freezing descriptions of what quantuum computing can do (trust me... it's freaky), then delves into what a computer is and how quantum computing may be applied. A must read for those who want to stay on the cutting edge of science or computing, but don't have time for four more years of school.

Rating:
Summary: Brain Freeze
Review: This book is well written, clear, and concise. It is also challenging, amazing, and, at times, difficult to understand. Johnson begins with some brain freezing descriptions of what quantuum computing can do (trust me... it's freaky), then delves into what a computer is and how quantum computing may be applied. A must read for those who want to stay on the cutting edge of science or computing, but don't have time for four more years of school.

Rating:
Summary: Quick, direct introduction to quantum computing
Review: This book was very useful in introducing me to the mechanics of quantum computing. Using simplified concepts and compartmentalized explanations, the book manages to explain the core concepts of quantum parallelized computing using tinkertoys, gears, and black-box algorithms.

I've had some previous introduction to quantum theory, but the limited depth provided by this book is exactly what I needed to base further exploratory reading on. It's a perfect "first" stepping stone for anyone interesting in exploring the field, either at depth or at leisure.

Rating:
Summary: -- Insert Superlative Here --
Review: This guy not only describes quantum computing in a way that should be accessible to nearly everyone, but he does it in a highly entertaining, highly readable way. By appealing to a healthy dose of abstraction, the author is able to seamlessly touch on an amazing array of topics from computational theory to quantum mechanics to cryptography. Occasionally he sinks deeper into the quantum quagmire to examine a few quantum algorithms, but he never loses sight of his intended audience: the scientifically curious layman.

This book does contain a large amount of hype, but to his credit the author includes the opinions of a few noteworthy skeptics to lace all the optimism with a sprinkle of doubt. If you are looking for a quantum appetizer, or to bring yourself up to speed on the buzz behind quantum computing, I couldn't recommend this book more highly.


Rating:
Summary: Child's play.
Review: 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. 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.

Rating:
Summary: A computer for the future
Review: Your computer will not so soon become outdated. If you have got the computer from HP or IBM, you will work quietly 5-10-15 years. I have the programmable calculator HP-67 and it solves the majority of electro technical tasks for me since 1977.

However all question that the law Moore's law naturally lags behind our computing needs , and in a number of cases it simply brakes scientifically technical progress. The progress, and the main tasks of a science and engineering are doubled for each year. Therefore I naturally use by the computer: Pentium 4, 1500 MHz.

Therefore concept qubits is rather urgent, is useful for a wide range of the readers. The speed of the decision of tasks has the large importance, but not always essential. For example I passing with the computer 286, 386, and 486 and so on and this step by step always tested inconveniences with recognition of the received information. My brain could not so quickly be prepared for its adequate and recognition of dates and information from a computer.

Hence the book of the author gives us an opportunity psychologically to be ready to new development. On the other hand, you are ready to understanding of new computing systems, which "do understand" a "difference" between the woman and steam locomotive, instead of it is simple to run "1" and "0" in a operative memory of the computer.

It is very healthy also thank to the author for increase of our technological level.

[e-mail]

Rating:
Summary: "He makes you smart and quantum computing real"
Review: Your computer will soon be out of date. You know that already, especially if you know about Moore's law, which was originated forty years ago, and says that every year and a half, the density of components on a computer chip will double. From the room-sized vacuum tube monsters down to the sprightly laptop, there has been a continued decrease in size and increase in speed. But silicon technology cannot reduce forever; it is still based on atoms, and it cannot get smaller than an atom. There is no law, however, that says we must forever be dependent on silicon, and so entirely new technologies may be developed. The technology, undeveloped but promising, which has interested physicists and computer scientists the most is quantum computing. We don't have quantum computers yet, and they aren't a sure thing, but the possibilities are tantalizing. George Johnson, a science journalist, has tried to make the new technology plain in _A Shortcut Through Time: The Path to the Quantum Computer_ (Knopf), and for those of us who aren't mathematicians, physicists, or computer scientists, he has done an admirable job at making a very strange, not-yet-practical technology understandable. Few of us need to know how silicon chips work, and fewer still will ever understand how quantum computers will work. Indeed, the quantum world is so vastly strange and counterintuitive that no one really can understand it. But Johnson's book is a good introduction to the strangeness, and a good vantage point from which to watch the upcoming revolution, if it comes.

Johnson's book is about a real quantum leap. The classical physics of our silicon computers does not hold within the tiny spaces inside atoms. Single particles at that scale can _really_ be in two places at once, and similarly, a quantum bit of information (known as a qubit) can be set to 1 and 0 at the same time, known as a "superposition." Qubits could be set to perform almost instantaneous calculations of huge programs, and there is no part of physics that says such computing should be impossible. Indeed, on the smallest of scales, primitive quantum computing has already been accomplished. Qubits are temperamental, and current research has to be done at supercold temperatures without the possibility of disturbance. Still, there is enormous intellectual interest in the prospect of quantum computing. One researcher in the field said that he and his colleagues are "writing the software for a device that does not yet exist." If quantum computing works, for instance, we will have to rethink all our current encryption methods, which are based on the difficulty of factoring large numbers; quantum computers do such things with ease silicon never can.

You aren't going to understand quantum computers by reading this book; Johnson knows that he is trying to describe the undescribable, and he makes it clear that he is no physicist, just someone trying to understand what all the fuss is about. His book is lucid and his descriptions do not bog down in technicalities (at times he gleefully hurtles over them). The book is also brief, but has enough substance to give even those who know little about current computing some basic understanding of where quantum computers may take us. He has successfully conveyed the excitement these potential gadgets have sparked, and readers will be able to participate in the excitement themselves.