The Age of Entanglement
by Louisa Gilder
Alfred A. Knopf, 2008

Perhaps there is no greater demonstration of Einstein's brilliance and famous independence than his rejection of the spookiness at the heart of quantum theory. Einstein recognized early that quantum mechanics plays a "risky game with reality", and the stakes are nothing less than our deep beliefs about cause and effect that make up the support beams holding science together as a coherent structure.

If you disturb a particle in the lab, how is it that your actions can have an instantaneous effect on another particle, entangled with the one you perturbed, but located halfway across the universe? This idea of instantaneous causality, defying the limits of spatial separation, was for decades the dirty secret of quantum mechanics, simply ignored by the physics community. Einstein's criticisms, instead of being taken seriously, were instead taken as evidence that Einstein was off his game.

Einstein wasn't alone. Irish physicist John Bell thought something was rotten at the heart of quantum mechanics, and it was his famous result, known as Bell's inequality, that helped reestablish quantum entanglement as a subject of polite discussion. Entanglement, for years the subject of thought experiments (including the famous ones of the Einstein-Bohr dialogue), became the subject of real experiments and now comprises the foundation of the hot science of quantum computing. The fascinating history behind entanglement has been neglected by writers of popular science histories, and thus Louisa Gilder's The Age of Entanglement is a welcome addition to the genre.

Gilder's strategy is to structure her book on the basis of Heisenberg's astute insight that "science is rooted in conversations." She writes that typical physics textbooks miss this essential ingredient of science; in them, "physics seems to be a perfect sculpture sitting in a vacuum-sealed case, as if brains, only tenuously connected to bodies, had given birth to insights fully formed." What makes science history so interesting is that "knowledge is built, one puzzle piece at a time, by people living their lives in specific times and places with specific passions." Conversations, most often informal ones taking place in group meetings over bagels, in break rooms over coffee, after conference sessions over beer, are critical to this process. For the historian trying to capture the long threads of argument that have culminated in great scientific successes, these off-the-cuff discussions are a valuable but elusive source of illumination of the intellectual pathways trod by great scientists.

The Age of Entanglement attempts to capture these unrecorded but important conversations with the potentially clever trick of taking snippets of writings and quotations by Bohr, Einstein, Heisenberg, Pauli, and others, and pasting these snippets into reconstructed conversations. Gilder makes a valiant attempt to get this device to work, but ultimately the device fails. The most immediate problem is that many of the reconstructed conversations have the feel of awkwardly-lit dramatic reenactments featured on 20/20 crime documentaries. The awkwardness of these conversations grows for the reader in cases where the participants have been extensively recorded in real life. Gilder's reconstructed Brazilian bar conversation between Richard Feynman and David Bohm comes off tinny when placed in contrast to the real-life Feynman whose style has been captured in hours of recorded lectures and documentaries.

Awkwardness aside, there is a more serious problem with these reconstructed conversations. At their worst, they become a crutch, a cut-and-paste substitute for analysis and narrative control by the author. When a conversation is recreated from written arguments made years later, important elements of context can get lost. The physicist and science writer Jeremy Bernstein, who interviewed many of the important players of quantum mechanics, took issue with how Gilder used one of his interviews, suggesting that she "added fictional gloss which distorts the context of these interviews." Instead of explaining the scientific arguments herself, Gilder frequently lets Bohr, Einstein, Heisenberg, Pauli, and the others speak through their writings, which sounds effective in theory, but in practice the scientific explanations get muddled. If you had no background in physics and were sitting in a street car eavesdropping on Bohr and Einstein, you'd be lost. At least in that case, you would likely recognize your confusion. The danger in the reenactments found in this book is that Gilder provides enough coherence to the conversations that many readers might think they are being let in on deep scientific insights, but more careful readers will find the recreated arguments unclear and imprecise.

I also was put off by the occasional touches of historical amateurism. Since historians have been scouring this ground for a long time, the bar is high for new historical claims. Gilder drops a potential bombshell - a quote from a declassified Soviet document, published in 2002, that suggests Robert Oppenheimer really may have passed atomic secrets to the Soviets. Gilder quotes from the document without comment, completely ignoring the fact that several superb Oppenheimer historians have persuasively debunked the document as evidence of espionage by Oppenheimer (see Bird and Shwerin's American Prometheus, p. 190-191, and David Cassidy's Oppenheimer and the American Century, p. 198-200). If Gilder wants to take on the best current Oppenheimer scholarship, she needs to do more that simply drop quotes.

Once Gilder leaves the already well-trod ground of pre-World War II quantum mechanics, her book really shines. The history of the first thirty years of quantum mechanics has been thoroughly worked over, but Gilder proves that the neglected last fifty years of quantum mechanics is just as full of brilliant, quirky personalities and mind-bending discoveries. She has conducted interviews with many of the key scientists who, by both theory and experiment, brought quantum entanglement out of the disreputable shadows of Einstein's disturbing debate with Bohr and transformed the subject into a respectable science.

Gilder skillfully describes the times, places and passions of those scientists. John Bell, with his plastic shoes (motivated by his vegetarianism), could playfully poke fun at his colleague Reinhold Bertleman's intentionally mismatched socks in order to creatively illustrate a point about quantum entanglement. Bell felt passionately about the blind eye which the physics community had turned towards the confusing and spooky implications of entanglement. In fact, entanglement was so disreputable that Bell had to treat his work on it as a secret hobby. This was work that would become one of Bell's greatest professional accomplishments.

The quest to experimentally test Bell's famous theoretical result is a story that has not been told often enough in the popular literature. Gilder has spent hours talking with the scientists who demonstrated the reality of entanglement, and she conveys a great sense of the excitement involved in pursuing pathbreaking science. We read about graduate students who turned from safe but pedestrian thesis projects to do something risky but genuinely new, about collaborations forged, and about the cajoling necessary to get the equipment and resources to do an experiment that most colleagues thought was a waste of time. One physicist, Ed Fry, was denied funding to do what later turned out to be an important experiment testing entanglement using a laser-based apparatus that was a significant improvement over previous experimental setups. Among the reasons for his rejection was that "time and money [were] already being wasted at Berkeley and Harvard" pursuing this crazy idea.

Entanglement is now an even more exciting subject than it was when Bohr and Einstein had their great debate. The subject didn't end with this clash of titans, and there are few other books out there that continue the story as engagingly Age of Entanglement. The book would have been strengthened had Gilder streamlined her treatment of the more familiar early history and incorporated more thorough explanations of the science into her narrative, instead of tacking these explanations on at the end as "longer summaries" of the science. But this is her first book. She is a very compelling writer, and she clearly understands what makes science exciting and science history interesting. In spite of my occasional frustration, I enjoyed this book, and I am eagerly looking forward to Gilder's next book.

For further reading:

Revisiting the Einstein-Bohr Dialogue, Don Howard

Programming the Universe, Seth Lloyd

Against Measurement, John Bell

Simulating Physics with Computers, Richard Feynman

Have you read The Age of Entanglement? Offer your comments! And join me for next month's Sunday Science Book Club on February 15th. The plan for this book club has changed; in honor of Darwin's 200th birthday, we'll be reading Edward Humes' Monkey Girl, the story of the Dover, PA Intelligent Design Trial - the Scopes trial of the 21st Century.

Front page picture courtesy of of Oak Ridge National Laboratory.