Customer Reviews

Entanglement

5 star:		(8)
4 star:		(5)
3 star:		(7)
2 star:		(0)
1 star:		(1)

 

 

This is one of the best books I've read this year. It's easy to read, highly informative, accurate and fun. Aczel has done a masterful job of combining a book on scientific history with an introductory tomb explaining one of the especially non-intuitive aspects of the quantum world - the entanglement of multiple quantum particles.

Entanglement as a consequence of quantum mechanics was actually predicted by Einstein and used in a thought experiment to try and discredit the new theory. Einstein believed in strict determinism and considered quantum mechanics to be incomplete. He had a lifelong friendship and debate with Bohr, who was one of the founders of quantum theory. Einstein, along with Podolsky and Rosen developed a "thought experiment" in which the outcome was so weird - if quantum physics was correct - that it simply couldn't be accepted (by Einstein, anyway). Einstein considered this weird outcome in quantum mechanics to essentially prove that it was incomplete.

In Einstein's thought experiment he imagined two entangled quantum particles whose quantum properties were dependent upon each other. For example, the particles could be photons produced by a reaction that starts out with zero spin. Since spin is conserved, and photons have integral spin, if one photon has spin +1 the other must have spin -1.

Quantum mechanics says that, until the particles are measured, their spins are in a superposition of states, and when one photon's spin is measured, the other photon instantly assumes the opposite spin - no matter how far apart the two are. Indeed, before they are measured, quantum mechanics doesn't treat the two photons as distinctly different particles at all. Before the measurement (before collapse of the wave function) they are a superposition - something for which there is no classical analog.

Quantum mechanics is thus non-local, and Einstein thought the result of this thought experiment, weird as it is, left no other option but to conclude that quantum mechanics is incomplete. The thought experiment proposed by Einstein, Podolsky, and Rosen was a serious challenge to Bohr and other scientists who subscribed to the Copenhagen view on quantum mechanics.

Years passed after Einstein proposed this experiment, and it remained technically out of reach. Later, the idea was refined by John Bell who showed that the central logical question in the EPR experiment can be reduced to an inequality that can be measured in actual experiments.

This is the story of how scientists built upon Einstein's initial idea of entanglement and used Bell's ideas to construct practical experiments to test one of the strangest ideas in quantum mechanics.

Einstein thought the non-local and fundamentally unpredictable nature of quantum mechanics was too weird to be true, but when scientists finally managed to test entangled particles, they found that they really do behave just as quantum physics said they would. Quantum mechanics really *is* weird, but only because it describes the universe, and the universe is weird.

This is a nice little book that does a good job of weaving the history with the science. I thoroughly enjoyed reading it, and highly recommend it.

Excellent history showing how much of the quantum weirdness was discovered. I really enjoyed the personal stories of the scientists that made these discoveries. However, not enough detail was given when it came to EPR and how the results pointed to non-local reality. Otherwise, it was a great read and well worth the money!

I should begin by saying that I was expecting (or hoping for) a different book, though perhaps from the other book by Aczel that I have read (Mystery of the Aleph), my expectations were probably misplaced. The book that I was hoping for would have been much more technical, though given the fact that only a handful of equations appeared in the book at all, this would not be difficult), and one that would explain what this entanglement thing is, or at least provide arguments for some of the prevailing theories.

What this book did provide, though, was a brief account of the history of entanglement as a controversial physical concept. I first encountered entanglement while doing some studies in quantum computation, and my studies were on the computer science/mathematical side, which basically meant that entanglement was a given, and it never really occurred to me that there would have been much controversy --- in retrospect, this was quite naive of me. By going through the breakthroughs made by many physicists over the passed century, Aczel was able to bring light to the fact that while science textbooks state principles as undeniable truths, doing science and interpreting science are more akin to a somewhat political struggle. For this reason, there is much to commend this book.

However, a great shortcomming is the length. The book is divided into 20 chapters with an average length of about 12 short pages. Most chapters have a two-fold purpose --- to introduce and give a brief biographical sketch (leaning more towards intellectual development) of someone involved in the history of entanglement, and also to explain briefly what that person did. Due to the length, it is impossible to provide much detail of either the person(s) introduced or how the result fits into the overall development of our understanding of the quantum world. The only results that seemed to permeate the book were the paper by Einstein, Podolsky and Rosen which introduced the concept as an argument against quantum physics, and John Bell's theorem which provided a theoretical mechanism to determine whether Einstein or quantum physics is correct.

After reading this book, I am looking forward to going through more books listed in the References, in the hopes of finding the book I want.

Amir Aczel's book "Entanglement" is a great introduction to the subject for the non-physicist, or the future physicist, in my case. As someone who is just starting out with his studies in physics, it was great to have the chance to read a book on a very complicated subject, written for a much wider audience than simply the people who work in that field.

Aside from the strangeness of the concept of entanglement itself, what I found fascinating was how the interplay of personalities, professional rivalries and the general direction of the field of physics lead to the startling suggesting of entanglement in the first place.

I applaud Aczel's accomplishment. It isn't easy to make something as strange as entanglement understandable to a scientifically untrained audience, but he has done so exceptionally well. This is much more a book about the history of the players involved than it is about the science itself, though both subjects are touched on with great style. A fascinating and entertaining read

I was fascinated by the topic of entanglement -- the quantum reality that particles separated by a distance can "communicate" with each other. Strange indeed, but the book provides experimental evidence supporting this unusual concept. I enjoyed the physicist's personal profiles that play a role in the history of entanglement, sometimes finding it a bit distracting from the scientific finding though. The diagrams of the experiments are a bit difficult to follow, the explanations too brief, and the attempts, occasionally to write "math equations" frustrating. I understand the need to write for the lay person, but the book falls short of those of us with some math background and physics knowledge. If only the book had illustrations equal say, to Scientific American, with equally good explantions, we would have a scientific bestseller. I enjoyed the book but it falls short of being really scientific.

At first the book appears entertaining -- but since its title specifically deals with one concept of quantum mechanics, I expected a thorough presentation of it. After a couple of hours reading it, I realized that there was not much precision in the description of almost all physical concepts. For example, I cannot see how can someone get any idea of what the Schrödinger's equation is all about by reading the author's description. When the author switch the "Schrödinger' cat" for Wheeler's cat I thought mainly of it as a joke -- but the author was probably serious; and I think he misunderstood the whole idea of "Schrödinger' cat". The author goes at length on biographical details of some physicists (e.g., Schrödinger) but without much content to the subject at hand, entanglement. It takes a while before the very subject of the book kicks in. About 150 pages out of 284 could easily be removed without disturbing much the physical descriptions. Although the biographical details of all the physicists make it an entertaining book -- but for precise physical details you will probably need another book while you read that one.

I thoroughly enjoyed this book. I am a layman with a deep interest in Physics, and have read many "popular" science books. This is my second Acxel book, and I am a fan.

The book provides a nice walk through the history of Entanglement and Quantum theory. Most of it is understandable to the layman, which probably means that a physics professional would find it overly simple. However, it is by no means an easy read.

I picked up this book with a single question in mind: "What is Entanglement?". Now that I've finished the book, I still don't know. I don't know what state entanglement is, or what causes it. But I do understand that the reason I don't have a nice, clear picture is that it does not yet exist. I know the science is controversial and why. And I do understand what is meant by "entanglement". I feel much more familiar and comfortable with the term, but know that there is much more to learn. I have some simple idea of how to proceed, so I'm happy with the book.

The book provides a lot of background on the people who were involved with the creation of the science. That is good, as such people deserve credit. But why do I need to know the religion of every person? I have a firm belief in God, but I really don't care if someone is Jewish, Christian, Muslim or otherwise. I find that their views and biases are much more useful, which was only lightly covered.

I picked up this book to help me try and understand entanglement from a beginners point of view. While I found the writing interesting,(especially about the various histories of those involved) I thought it was not clear enough in explaining the the concept of the two slit experiment, and the more general concepts of quantum theory. This book is better as an accessory book in dealing with the history of quantum mechanics. A book that is more helpful is "The New Quantum Universe" by Hey and Walters. Still, the writing is good, and I'm glad I picked it up. Once I find a book or books to explain these concepts better to a beginner such as myself, I'll return to this one to savor the history of the people involved.

Can two particles become linked, so that a change in one is instantly reflected in its counterpart, even if a universe separates them?

Amir D. Aczel tries to give an answer in his book 'Entanglement'. The first two thirds of the book covers a history of Quantum Physics and all its famous scientists. For someone, who is interested in how it all started this is a very good introduction into the works and live's of all the founders of Quantum Physics.

The last third of this book finally addresses one of the biggest mysteries in Quantum Physics - `Entanglement'. Even as `Entanglement' is just in its beginning of exploration we are already seeing the first practical applications in form of cryptography for secure communication.

Review posted also on my website at:
<a href="http://www.quantumbiocommunication.com">Quantum Biocommunication Technology</a>

Like Aczel's other books "entanglement" goes unusually deep into the subject. Most popular books on physics patronize the reader and consider they have done their job if they have "explained" the concepts.

Aczel treats the subject and the reader with the reverence they deserve. Nobody understands quantum mechanics completely. All we know for sure is that it is "stranger than we can imagine."

My favorite part was about the photons that go through a nonlinear crystal and split into two photons whose frequencies add up to the frequency of the original. The two photons are doubly entangled and "it is not understood scientifically" why the splitting happens. Only one in 10 billion photons split. Clearly an example of the old adage that anything not specifically forbidden by the laws of quantum mechanics will eventually happen. (But this is not an explanation.)

I would just mention two developments not covered in the book.

1. Ahronov's Weak Measurement makes it possible to measure the state of a particle without disturbing it. See the Wikipedia article. Therefore Quantum Cryptography is not as secure as once thought.

2. Retrocausality, as discussed by Ahronov, Huw Price and others can be invoked to remove the paradoxical effects of the EPR experiments. If you allow a limited amount of backward-in-time causation, which the equations of quantum mechanics do allow, then no spooky action-at-a-distance is needed and hidden variables can exist. This is a minority view at the moment, but that may change.