Customer Reviews

MINDS, MACHINES, AND THE MULTIVERSE: THE QUEST FOR THE QUANTUM COMPUTER

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1 star:		(2)

 

 

A wonderful overview of the history and science of this extraordinary new discipline. Brown's documentary approach interlaces explanations of quantum computers with comments from the pioneers of this field including David Deutsch and Richard Feynman. It makes for riveting reading with many witty asides thrown into some far-sighted discussions of where the subject is leading. David Deutsch comes across as a true visionary even if his ideas concerning multiple universes sound far-fetched. Rather like Penrose's, "The Emperor's New Mind", Brown caters for multiple tastes by writing for a general audience but adding (mostly in appendices) some mathematical explanations and circuit diagrams. These can be can be safely skipped without losing the narrative thread. A pity to do so though because his explanations are a delight. Thoroughly recommended.

I read "Minds, Machines, and the Multiverse" (reprinted in paperback as "The Quest for the Quantum Computer") alongside David Deutsch's "The Fabric of Reality," thinking that Julian Brown's journalism would help elucidate Deutsch's text, which I assumed would be more difficult. Ironically, not only did I find "The Fabric of Reality" far more exciting and readable, but, even on its own terms, Brown's book was often monotonous and unimaginative.

While the first and last chapters are quite fascinating, the meat of the book reads like an endless serious of abstracts of articles excerpted from mathematical, physics, and computing journals, separated by droll subheads ("Beam Me Up, Atom by Atom"). The major problem is that Brown doesn't seem to have any particular audience in mind. On the one hand, it's hard to imagine most lay readers sitting through his detailed expositions on various mathematics and physics concepts; on the other, math-savvy readers don't need to be told (to cite just one example) what ASCII is.

It's not just that Brown's book is knee-deep in mathematics, however. In fact, the math presented is really not that difficult--it's just boringly presented. The endless series of Alice, Bob, Carol, and Eve stories has all the verve of the litany of questions on the SAT. (Several times I found myself asking, "Which Bob is this?"). Likewise, the descriptions of logic gates are about as exciting as my college textbooks on linear algebra and number theory. Brown's presentation is hampered further by the lack of a glossary; he repeatedly expects the reader to remember terms he discussed over 100 pages earlier.

In sum, computer programmers and armchair mathematicians looking for a primer on the theoretical underpinnings of quantum computation might find this book a helpful introduction. The general reader, however, will have to wait for a well-written overview of the subject. In the meantime, I recommend "The Fabric of Reality" as a starting point.

But didn't. It tries really hard and has a noble goal, but I think falls quite short. This is a topic that I am quite passionate about and was one of the first books on the topic. At the end of reading this book you will have very many more questions and unfortunately very few clear ideas about the workings or theory of quantum computers. Over and again Brown stops just before giving you the details that you hope for. I've actually found David Deutsch's papers on quantum computing (at qubit.org) almost as accessibe and much more informative than this book, not to mention that they are much more concise.

If you're hoping to get a basic grasp of quantum computing, read John Gribben's "In Search of Schrödinger's Cat" for a non-technical crash course in quantum mechanics and then head for the scientific papers.

This book fails to gauge what a reader will be able to understand. This is a difficult task at times, but when writing "popular science" the author must choose a level to present the material at. Unfortunately in parts that aren't particularly interesting the author pushes this only to retreat at a point where things are getting interesting. You're left feeling, "No, really. I can take it!"

This is the book I recommend to all my technical friends who are wondering what quantum computing is about. Brown writes with astonishing lucidity and an intense focus on what he's trying to communicate. If this book has a flaw, it's that I think it gives Deutsch and the many-universes interpretation of QM a bit too much airtime. Deutsch's views are well-presented in many other places and it dilutes this book somewhat to spend so much time on him when it really isn't necessary.

I don't understand the review that said this book wasn't technical enough. Yes, it's not a textbook for learning how to write quantum algorithms. But it does have detailed quantum circuit diagrams for a number of useful or interesting ones. When I read this book I finally saw enough of the details to "get it". I launched from this directly into the scientific literature without getting too terribly lost.

I would recommend this book over Milburn's "The Feynman Processor". Milburn knows his material but he tends to wander a lot. His book is OK and useful, but this one is better. I'd put it in the same class as Gleick's "Chaos".

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.

This is the kind of popular science book I would like to see more often. Most popularizations skim over the surface of their subjects without providing enough detail to understand what is really going on. In this book, the author has done a remarkable job in mixing amusing and fascinating anecdotes with philosophical and technical details. His discussion of the evolution of quantum theory is one the best I've read and cleverly interpretated from a computational viewpoint clarifying the link between quantum mechanics and computers - a surprising connection that few quantum theorists imagined until the 1990s...This is an excellent book and one that builds very succesfully on David Deutsch's 'Fabric Of Reality'.

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.

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.

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.

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