Rating: 
Summary: The best overview of Quantum Computing I've seen...
Review: In The Quest for the Quantum Computer, Julian Brown takes a look at the emerging field of Quantum Computing, a field that could potentially revolutionize many fields of computing and far-edge technology, such as cryptography, information theory, higher mathematics, and nanotechnology.So what is a Quantum Computer, anyway? A Quantum computer, in Brown's term (derived from the work of David Deutsch and Richard Feynman), is a computer based on an atom-scale architecture that, rather than using standard digital logic gates, uses logic gates based on "qubits", or quantum bits, that can carry a bit with a value of 1, 0, or any position that could theoretically exist in between. Such a computer could be used to process massive matrices of information in paralell, and solve mathematical problems previously thought impossible to answer. Still following? If not, the book isn't for you. It's quite dense, and filled with logical and mathematical jargon- it was clearly intended to be a "popular" book for a select audience- people with physics, engineering, mathematics, and computer science backgrounds. But if you're interested in "the new physics", on-the-edge computing, or future technologies in general, pick this book up.
Rating: 
Summary: The Other Me's Read It and Liked It I think
Review: it seems that in one of the multiverses that surround me like a fog these days, another 'Me' has already read this book. What seems to bug this other 'Me' about the book, is the tacit assumption that such superpositions are *never* experienced in the 'classical' world. Well, jeez, what else is schizophrenia all about, eh? And if you read some of the old Zen Master anecdotes, they are clearly talking about living in a world of superposition, where 'to go one mile east, is to go one mile west'. What we need is for Thomas Cleary to have a go at doing a syncretic synthesis of Zen and Physics. It's about time for a newer 'Tao of Physics' it seems to me!
Rating: 
Summary: Ideal for the non-specialist general reader.
Review: Julian Brown's Minds, Machines, And The Multiverse documents the search for the quantum computer, which promises to change not just technology and science, but how we understand forms of reality. Imagine a computer in which speed is increased because of how it juggles jobs, taking seconds to perform calculations which would take the best supercomputers longer than the age of the universe to complete. Technical details are presented in surprisingly simple form so lay readers can readily absorb the information.
Rating:
Summary: Alison's review of Minds, Machines, and the Multiverse
Review: Minds, Machines, and the Multiverse explores the many issues of a quantum computer. Even though a quantum computer has never been built, the idea of one has been around since the beginning of the 20th century, and several theories about a quantum computer have surfaced. The implications of such a machine would mean profound advances in cryptology and code breaking, low-energy computing, cloning, nanotechnology, and possibly even computers that are smarter than human beings. Brown illustrates very well how technology is growing at a rapid rate. Transistors will require less and less electrons to function, and eventually we will need to use a single electron or an alternate system altogether. This new system may be found in Quantum mechanics. According to the book, in an atom an electron can find itself in the ground state and the excited state simultaneously; this term is called superposition. So, a quantum bit, or qubit, can store values between a "0" and a "1". This superposition is unlike digital bits because a digital bit can only store a "0" or a "1". With this superposition, a small number of qubits can store more information with an infinite number of different superpositions we can make. The book explains how this superposition attributes to the new theory of quantum computers. Quantum computing is the idea that a computer can work on several different problems at one time; this is also known as parallelism. Whereas now our computers have to do one thing at a time, a quantum computer could do endless jobs simultaneously. If quantum computers are ever made, they will probably be used only for certain special tasks such as mega-information processing. Another necessary function of the quantum computer, according to Brown, is the ability to use much less energy than computers do today. By having the computer reverse itself after each calculation, it saves itself energy by not having to store and erase unwanted information, or "trash". Therefore, once you get it started it "just coasts". As stated by the book, a quantum computer could solve a very important mathematical problem by calculating the factors of very large number extremely fast. This threatens to expose the world's most sophisticated secret codes. If anyone could build a quantum computer, they could access the most protected information, even from our federal government. It is funny how Brown notes that, "It is no surprise, then, that significant funds backing this line of research have come from such organizations as the U.S. Department of Defense, the National Security Agency, NATO, and the European Union." Brown writes that Nanotechnology is a technology that is expected to arrive on the scene around the same time as quantum computers. It involves storing a bit of information on a cube of 125 atoms. With this miniscule storage capability you could write the entire contents of the Encyclopedia Britannica on the head of a pin. Theorists state that around this point computers will become smarter than human beings, and they could begin to redesign themselves. This predicted revolution has been named the singularity. While this book seems to be more science fiction than computer science, I found it to be informative and very interesting. Our technology seems close to hitting a wall where something has to give. Whether that means the "singularity", quantum computers, or just computers that use less energy, it will be fascinating to see what happens.
Rating:
Summary: Nice job
Review: One of the hottest topics in foundational research in quantum physics at the present time, and of overriding importance technologically, quantum computation will no doubt remain as a tour de force in years to come. The author does a fairly good job of summarizing the history and background of the theory and experimental situation in quantum computation. It is written for the layman but the author does not hestitate to interject some elementary mathematics. The author does a good job of overviewing the relevant physics, but exaggerates sometimes certain experimental results, in particular, the experimental verification of entanglement. David Deutsch, well-known in the theory of quantum computation and foundations of physics, gives a superb forward to the book. He deplores the situation of not encouraging criticism of accepted truths that he sees occuring in most universities. I think he is correct in most respcts, as such an attitude is very manifested in the current attitude on quantum entanglement: it is taken to be axiomatic that such a concept has been experimentally verified by most in the field. The first chapter gives a brief overview of what is ahead in the book, and what a quantum computer could do if constructed, and a little history behind the research on quantum computing. A discussion of Shannon information theory and Landauer's principle is given in the next chapter. The later is supposed to allow one to get away from the kT minimum energy requirement for each unit of computation, using a concept of logical irreversibility. The double-well scenario he describes though is a little suspect, since if viewed from the standpoint of quantum field theory the barrier will effectively disappear because of quantum interference. DNA computers, the Fredkin gate and the the billiard computer follow as examples of reversible computers. The billiard computer should be definitely classified as a thought experiment, for one can show that such a system is chaotic, nullifying its utility for computation (at least in the ordinary sense of computation). A more promising approach, via cellular automata, is discussed. It was refreshing to see that Paul Benioff's theories were discussed in this book, as his results were the first meaningful attempt to model classical computation by using quantum physics. I read Benioff's papers in 1990, eleven years after they were first published, my interest being somewhat different, namely that of studying the suppression of classical chaos by quantum fluctuations. Benioff was concerned with the effect of quantum fluctuations on classical computation, i.e. would the efficacy of a classical computer be reduced at the quantum level? In attempting to explain the construction of a quantum computer, the author does a good job of describing some of the important operations that act on quantum states, such as quantum rotations and Hadamard transformations. The work of Peter Shor, who received a Fields Medal for his "quantum" algorithm that factors numbers efficiently, is described in the book, and the author in this discussion introduces the reader to some elementary ideas in cryptography. This is followed by an excellent overview of the field quantum cryptography. Unfortunately, the discussion is limited to quantum encryption schemes that are based on quantum entanglement, the latter of which has no sound experimental foundation. The author also does a fine job of discussing the role of decoherence in "messing-up" the operation of a quantum computer. The time scales involved in decoherence are something that has been the subject of much interest, and will no doubt be of the deciding factor in making quantum computation a workable idea. Ion trap, cavity quantum electrodynamics, and nuclear magnetic resonance have been studied intensively as candidates for quantum computers, and the author details nicely the current experimental situation in these approaches. The role of quantum error correction is also detailed in the book, and the author introduces the reader to what can be done with to do fault-tolerant computation. The Greenberger-Horne-Zeilinger experiment is presented in the context of NMR, but the author remarks that the nonlocal features of the GHZ experiment cannot be tested using NMR techniques, and so other approaches must be used. The Grover algorithm, and its power in database searching, is discussed also. The author ends the book appropriately with speculations and best-guess predictions on the future of quantum computing. One can only hope that quantum computers will be normal parts of the computing scenery in this century, and this book does show effectively the intensity in the research efforts to bring it about. With some justification though one could wonder why the adjective "quantum" is used to describe this form of computing at all. It is one thing to describe a concept using the formalism of Hilbert spaces, it is quite another thing to justify that this concept is actually physical. The geometry of Hilbert space does result in peculiar predictions for physical phenomena, but there are many other constructions, in mathematics for example, that are based on Hilbert spaces but have no physical analog. Perhaps, we should all refer to the theory of computation expounded in this book as "Hilbert space computation", rather than quantum computation. Such a description would free those interested to not think of physics as computation, but instead to construct a computer that is far better in performance than the ordinary "classical" one, but whose theory of computation and logic is based on Hilbert spaces, and not ordinary logic. The goal then would be to construct a real working example of such a computer....it might not be one that has anything to do with (traditional) quantum physics.
Rating:
Summary: An accessible guide to Quantum Computers
Review: Some books are just out there like a beacon.
And obviously Julian Browns Minds, Machines and
the Multiverse is such a book. If you want
an accessible guide to the rapidly evolving field
of quantum computers, this is the book to buy. Brown bedazzle the reader with the number of ideas
he comes up with on almost every page. All ideas somehow
connected under the headline Quantum Computers.
Quantum computing seems to connect computing and
physics in an explosive way. Thought, life and knowledge
these are computational things, whereas the
universe in at its most fundamental level is
physics. So obviously there is a lot to talk about.
And the book does so very elegantly, without ever
loosing track of the fact that this is a book
about quantum computers. Starting the book I was a bit worried that the book
wouldn't provide a sufficient level of detail about
the quantum computers and instead indulge in
too much speculation. After reading the book I think
it balances factual information with speculation
just right. Ok, Some might want to obtain additional details on
Peter Shors way to factor numbers efficiently on
a quantum computer. The intricacies of NP-complete
problems and quantum computers could have been
explored more. Some of the circuit analysis
could have been dealt with in even greater detail.
And why not write a complete book on competing
technologies for how to build an actual quantum
computer with actual live qubits? But I guess the book wouldn't have been such a
fine introduction then. Now, The presentation is well
balanced and demonstrates a thorough grasp over
all the many details in the field of quantum computing.
Fascinating general insights on math, computing
and physics makes it a great and insightful read. -Simon
Rating:
Summary: Julian Brown's Minds, Machines, and the Multiverse
Review: The editors and other reviewers have done a good job on this book, and I will just make a few comments. I've been working on quantum computers and quantum cryptography, but I'm very oriented toward how non-experts will understand books and articles. I don't think that there is any clearer book on quantum computers than Julian Brown's, but I agree with some of the others that it will still be hard to come away with a feeling of understanding some basic ideas of the subjects. This book is, however, excellent for the fascinating history of discovery and invention, which Brown excels at revealing. Just as you don't have to know much about law to enjoy biographies of politicians, you'll probably enjoy Brown's book very much if you don't expect too much from it. It's also a good opportunity for parents to teach children (and vice versa!) to love learning and knowledge, because if you tolerate and even not get upset at a certain level of ambiguity, you just might be tempted to read a few sections over a few times and then start looking on the internet or in the libraries for more details. Scientific American can help you to get more details on some of the things that you don't understand, and I wouldn't be surprised if one of these days a clearer book on the technicalities will also come out - in which case it will help you to be ahead of the game by reading as much as you can of this book. Research in the physical/mathematical sciences which is in the very new stages tends to be difficult to write up. Quantum computers and cryptography are about as new as research gets. The best creative geniuses probably are capable right now of writing up their ideas in English in such a way that most people would understand them if they try, but they're sort of in the position of a fireman who has to keep putting out fires rather than write his autobiography. The autobiographies and the clarifications will come later. One thing that you can do is to try to puzzle out who the most creative geniuses are from the book. There usually are only relative few in science/mathematics. Most scientists tend to be Ingenious Followers, just moving one step ahead of the last scientist. The Creative Geniuses jump many steps ahead, and they usually do it often. I'll give you a clue - one of the latter is David Deutsch of Oxford University's Clarendon Laboratory. Generally speaking, Great Britain and France and Belgium and the words Creative Genius in Physics/Math/Computers go together. I'm going to let you find the clues for the other Creative Geniuses for yourselves, except to mention for example that some of it has to do with Rolf Landauer of IBM's Thomas J. Watson Research Center, who passed away in 1999 just before the book was written. You might also be surprised to find that Professor Richard Feynman of Caltech borrowed somebody else's ideas (at least John von Neumann gave people credit when he did that) - Paul Benioff's of Argonne National Labs in Illinois. Look those people up on the internet and in books and journals. Also, look up entanglement and interference in the book's index and read all the pages about them in the book - the easiest ones first perhaps. I'll just leave you with a thought (I may give some more clarifications another time). Quantum entangled people will behave exactly the same even if they are in different galaxies. It's like the *psychic twins*. If that isn't enough to turn one toward a career in science/math, I don't know what is.
Rating: 
Summary: Could be interesting, but WAY over my head . . .
Review: The idea of a quantum computer is quite fascinating. Since a colleague of mine studied quantum computing at Oxford, I thought I might read up on the subject. My expectations were that "The Quest" would be something that would get the lay reader up to speed. I don't mind being stretched a bit (I have a Ph.D. in chemical engineering), but the book was just way too over the top for any not intimately familiar with quantum physics. The book contains a lot of interesting information, but it is sandwiched between some very difficult concepts and nomenclature. Remember, "know your audience . . ."
Rating:
Summary: Incredible Shrinking Computers
Review: The sudden appearance of a new branch of knowledge on my radar screen took me by surprise, and in skulking about to find out what was afoot I found this book extremely good as an introduction, surprised at the number of things that are brought together under one umbrella, information theory, quantum mechnizations through its spectrum of interpretations including Bell's theorem, the many universes version of QM of David Deutsch, and much else. Highly useful introductory account.
Rating:
Summary: Choose your worlds carefully...
Review: This is a decent sequel to David Deutsch's Fabric of Reality. Unlike much of the contemporary scene, this book doesn't dumb itself down for the lowest common denominator. The nice thing about this book though, is that while it gets down into the nitty gritty you can still follow along at whatever level you are at. Some people might give a ho-hum about quantum computers but once these people get past their own inertia they will be compelled to accept just how profoundly quantum computers will change our current collective conceptual framework. Also, at a little over half way through this book you might begin to wonder where the Mind part fits in with the Machine and Multiverse parts but by the final lines everything slips snuggly into place. Perhaps the only disappointment, which is surely not the book's fault, is that quantum computers are still only ideas not actualities. However exciting this topic may be, it is a topic about the near future, not the present, and so we are naturally left wanting more.
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