All that lay far in the future when Bell was puzzling through his short paper back in the early 1960s. Bell worked out his theorem not at CERN, but while on sabbatical in the United States. Indeed, he later recalled that it was only in the United States—where so few physicists showed any signs of interest in such topics—where he could achieve the isolation required to push through his thoughts and write up his papers. Bell left CERN in November 1963—arriving in the United States one day after John F. Kennedy had been assassinated, as it happened—and spent the year visiting the Stanford Linear Accelerator Center, the University of Wisconsin at Madison, and Brandeis University near Boston. He completed his review article on hidden variables first, and mailed it off to the Reviews of Modern Physics, in whose editorial office the manuscript mysteriously vanished, leading to an unheard-of two-year delay in its publication.20
FIGURE 2.4. John S. Bell in his office at CERN, 1982. (Courtesy CERN.)
At Brandeis he completed his second paper, “On the Einstein Podolsky Rosen paradox,” containing his proof that quantum mechanics cannot be squared with locality. At the time, authors had to pay steep fees to cover the cost of publishing their articles in the venerable Physical Review, long the standard-bearer among the world’s physics research journals. Bell was too shy to ask his American hosts to pay for an article so far removed from their research interests. So he submitted it to a brand-new journal with the curious title Physics Physique Fizika. Not only did the new journal waive page fees, but it actually paid authors to publish there—although the honoraria turned out to be nearly equal to the cost of ordering reprints. The journal’s editors had high hopes that their new venture would help alleviate the information overload and hyperspecialization then afflicting the field, comparing it to a general-interest magazine like Harper’s. In their opening editorial, the editors pledged to “try their very best to present a selection of papers which are worth the attention of all physicists.” Bell’s article appeared in the third issue of the fledgling journal, in November 1964.21
And then…nothing. No activity or acknowledgment whatsoever. Bell’s paper, deemed worthy of “the attention of all physicists” by the journal’s editors, did not receive so much as a single citation in the literature for four long years—and then it was passing mention in a one-page article. Slowly, slowly, citations to Bell’s paper began to appear, like the irregular clicks of a Geiger counter: six in 1971, seven in 1972, three in 1973. A burst of sustained activity began only in 1976, when twenty to thirty new articles on the topic began to appear each year. By 1980, a quite respectable 160 articles had been published in the physics literature on Bell’s theorem.22
During the mid-and late 1970s, pockets of interest coalesced, usually led by physicists who held a longtime interest in hidden variables and the interpretation of quantum mechanics. An active group emerged around hidden-variables theorist David Bohm, whose long journey following his McCarthy-era dismissal from Princeton had ended with him settled at Birkbeck College in London, following hops and skips to São Paulo, Brazil; the Technion Institute in Haifa, Israel; and Britain’s Bristol University. A separate group clustered around Louis de Broglie and Jean-Paul Vigier in Paris; and a third group, spearheaded by Franco Selleri, shuttled among Bari, Catania, and Florence in Italy. Most of these physicists had been working on hidden variables and the interpretation of quantum mechanics for decades; Bell’s theorem appeared an obvious extension of their long-standing interests. Acknowledgments in these many articles show a tight fabric of social interactions: members of each of these groups knew each other, frequently traded tips and critiques, and saw each other’s latest papers as preprints long before they appeared in the journals. By 1980, in other words, an “invisible college” devoted to Bell’s theorem had emerged, with centers of activity dotted throughout Western Europe.23
Surprisingly, the largest share of articles on Bell’s theorem during this period came from physicists working in the United States—27 percent of all the articles, in fact, compared with 7 percent, 14 percent, and 19 percent from authors based in Britain, France, and Italy, respectively. All this despite the absence of any deep interest in foundational topics on American soil, hidden variables or otherwise. Nearly three-quarters of these U.S.-based articles (72 percent), meanwhile, came from regular participants in the Fundamental Fysiks Group, the earliest sessions of which had been devoted to Bell’s work and quantum nonlocality. (If one includes authors who acknowledged help from members of the Fundamental Fysiks Group, the proportion rises to 86 percent.) Members of the ragtag discussion group proved to be among the most prolific early authors on Bell’s theorem in the world. Against all odds, the earliest champions of Bell’s theorem congregated in that most unphilosophical of spaces: a large seminar room in the Lawrence Berkeley Laboratory.24
Chapter 3
Entanglements
The Fundamental Fysiks Group grew fast…. We played a big role at the laboratory, but never an acknowledged role.
—George Weissmann, 2008
Members of the Fundamental Fysiks Group followed twisting paths to Bell’s theorem. Most were members of the Sputnik generation, and their careers had begun to unfold in the usual way. They had been drawn to the big metaphysical questions at the heart of modern physics, only to find their coursework crushingly pragmatic. Many graduated just as the bottom fell out of the physics profession, thwarting their expected career trajectories. One way or another they made their way to Berkeley, and to each other.
Group members’ experiences map larger features of the professional terrain as physicists’ Cold War bubble burst. The sheer variety of their experiences and the fast pace of change illuminate what daily life was like for young physicists caught in the tumult of the late 1960s and early 1970s. Their research interests, job prospects, and even senses of themselves and of what a life in physics could mean were refracted through an unusually turbulent time. Though they arrived at the Fundamental Fysiks Group by different routes, they shared a faith that deep philosophical questions, such as the implications of Bell’s theorem and quantum entanglement, were worth asking.1
John Clauser sat through his courses on quantum mechanics as a graduate student at Columbia University in the mid-1960s, wondering when they would tackle the big questions. Like John Bell, Clauser quickly learned to keep his mouth shut and pursue his interests on the side. He buried himself in the library, poring over the EPR paper, Bohm’s articles on hidden variables, even Hans Freistadt’s early review article. Then in 1967 he stumbled upon Bell’s paper in Physics Physique Fizika. The journal’s strange title had caught his eye, and while lazily leafing through the first bound volume he happened to notice Bell’s article. Clauser, a budding experimentalist, realized that Bell’s theorem could be amenable to real-world tests in a laboratory. Excited, he told his thesis advisor about his find, only to be rebuffed for wasting their time on such philosophical questions. Soon Clauser would be kicked out of some of the finest offices in physics, from Robert Serber’s at Columbia to Richard Feynman’s at Caltech. Bowing to these pressures, Clauser pursued a dissertation on a more acceptable topic—radio astronomy and astrophysics—but in the back of his mind he continued to puzzle through how Bell’s inequality might be put to the test.2
Before launching into an experiment himself, Clauser wrote to John Bell and David Bohm to double-check that he had not overlooked any prior experiments on Bell’s theorem and quantum nonlocality. Both respondents wrote back immediately, thrilled at the notion that an honest-to-goodness experimentalist harbored any interest in the topic at all. As Bell later recalled, Clauser’s letter from February 1969 was the first direct response Bell had received from any physicist regarding Bell’s theorem—more than four years after Bell’s article had been published. Bell encouraged the young experimenter: if by chance Clauser did manage to measure a deviation from the predictions of quantum theory, that would “shake the world!”3
Encouraged by Bell’s and Bohm’s responses, Clauser realiz
ed that the first step would be to translate Bell’s pristine algebra into expressions that might make contact with a real experiment. Bell had assumed for simplicity that detectors would have infinitesimally narrow windows or apertures through which particles could pass. But as Clauser knew well from his radio-astronomy work, apertures in the real world are always wider than a mathematical pinprick. Particles from a range of directions would be able to enter the detectors at either of their settings, a or a'. Same for detector efficiencies. Bell had assumed that the spins of every pair of particles would be measured, every time a new pair was shot out from the source. But no laboratory detectors were ever 100 percent efficient; sometimes one or both particles of a pair would simply escape detection altogether. All these complications and more had to be tackled on paper, long before one bothered building a machine to test Bell’s work. Clauser dug in and submitted a brief abstract on this work to the Bulletin of the American Physical Society, in anticipation of the Society’s upcoming conference. The abstract appeared in print right before the spring 1969 meeting.4
And then his telephone rang. Two hundred miles away, Abner Shimony had been chasing down the same series of thoughts. Shimony’s unusual training—he held PhDs in both philosophy and physics, and taught in both departments at Boston University—primed him for a subject like Bell’s theorem in a way that almost none of his American physics colleagues shared. He had already published several articles on other philosophical aspects of quantum theory, beginning in the early 1960s.5 Shimony had been tipped off about Bell’s theorem back in 1964, when a colleague at nearby Brandeis University, where Bell had written up his paper, sent Shimony a preprint of Bell’s work. Shimony was hardly won over right away. His first reaction: “Here’s another kooky paper that’s come out of the blue,” as he put it recently. “I’d never heard of Bell. And it was badly typed, and it was on the old multigraph paper, with the blue ink that smeared. There were some arithmetical errors. I said, ‘What’s going on here?’” Alternately bemused, puzzled, and intrigued, he read it over again and again. “The more I read it, the more brilliant it seemed. And I realized, ‘This is no kooky paper. This is something very great.’” He began scouring the literature to see if some previous experiments, conducted for different purposes, might already have inadvertently put Bell’s theorem to the test. After intensive digging—he came to call this work “quantum archaeology”—he realized that, despite a few near misses, no existing data would do the trick. No experimentalist himself, he “put the whole thing on ice” until he could find a suitable partner.6
A few years went by before a graduate student came knocking on Shimony’s door. The student had just completed his qualifying exams and was scouting for a dissertation topic. Together they decided to mount a brand-new experiment to test Bell’s theorem. Several months into their preparations, still far from a working experiment, Shimony spied Clauser’s abstract in the Bulletin, and reached for the phone. They decided to meet at the upcoming American Physical Society meeting in Washington, DC, where Clauser was scheduled to talk about his proposed experiment. There they hashed out a plan to join forces. A joint paper, Shimony felt, would no doubt be stronger than either of their separate efforts alone would be—the whole would be greater than the sum of its parts—and, on top of that, “it was the civilized way to handle the priority question.” And so began a fruitful collaboration and a set of enduring friendships.7
Clauser completed his dissertation not long after their meeting. He had some downtime between handing in his thesis and the formal thesis defense, so he went up to Boston to work with Shimony and the (now two) graduate students whom Shimony had corralled into the project. Together they derived a variation on Bell’s theme: a new expression, more amenable to direct comparisons with laboratory data than Bell’s had been. Even as his research began to hum, Clauser’s employment prospects grew dim. He graduated just as the chasm between demand and supply for American physicists opened wide. He further hindered his chances by giving a few job talks on the subject of Bell’s theorem. Clauser would later write with great passion that in those years, physicists who showed any interest in the foundations of quantum mechanics labored under a “stigma,” as powerful and keenly felt as any wars of religion or McCarthy-like political purges.8
Finally Berkeley’s Charles Townes offered Clauser a postdoctoral position in astrophysics at the Lawrence Berkeley Laboratory, on the strength of Clauser’s dissertation on radio astronomy. Clauser, an avid sailor, planned to sail his boat from New York around the tip of Florida and into Galveston, Texas; then he would load the boat onto a truck and drive it to Los Angeles, before setting sail up the California coast to the San Francisco Bay Area. (A hurricane scuttled his plans; he and his boat got held up in Florida, and he wound up having to drive it clear across the country instead.) All the while, Clauser and Shimony hammered out their first joint article on Bell’s theorem: each time Clauser sailed into a port along the East Coast, he would find a telephone and check in with Shimony, who had been working on a draft of their paper. Then Shimony would mail copies of the edited draft to every marina in the next city on Clauser’s itinerary, “some of which I picked up,” Clauser explained recently, “and some of which are probably still waiting there for all I know.” Back and forth their edits flew, and by the time Clauser arrived in Berkeley in early August 1969, they had a draft ready to submit to the journal.9
Things were slow at the Lawrence Berkeley Laboratory compared to the boom years, and budgets had already begun to shrink. Clauser managed to convince his faculty sponsor, Townes, that Bell’s theorem might merit serious experimental study. Perhaps Townes, an inventor of the laser, was more receptive to Clauser’s pitch than the others because Townes, too, had been told by the heavyweights of his era that his own novel idea flew in the face of quantum mechanics.10 Townes allowed Clauser to devote half his time to his pet project, not least because, as Clauser made clear, the experiments he envisioned would cost next to nothing. With the green light from Townes, Clauser began to scavenge spare parts from storage closets around the Berkeley lab—“I’ve gotten pretty good at dumpster diving,” as he put it recently—and soon he had duct-taped together a contraption capable of measuring the correlated polarizations of pairs of photons. (Photons, like electrons, can exist in only one of two states; polarization, in this case, functions just like spin as far as Bell-type correlations are concerned.) In 1972, with the help of a graduate student loaned to him at Townes’s urging, Clauser published the first experimental results on Bell’s theorem.11 (Fig. 3.1.)
Despite Clauser’s private hope that quantum mechanics would be toppled, he and his student found the quantum-mechanical predictions to be spot-on. In the laboratory, much as on theorists’ scratch pads, the microworld really did seem to be an entangled nest of nonlocality. He and his student had managed to conduct the world’s first experimental test of Bell’s theorem—today such a mainstay of frontier physics—and they demonstrated, with cold, hard data, that measurements of particle A really were more strongly correlated with measurements of particle B than any local mechanisms could accommodate. They had produced exactly the “spooky action at a distance” that Einstein had found so upsetting. Still, Clauser could find few physicists who seemed to care. He and his student published their results in the prestigious Physical Review Letters, and yet the year following their paper, global citations to Bell’s theorem—still just a trickle—dropped by more than half.12 The world-class work did little to improve Clauser’s job prospects, either. One department chair to whom Clauser had applied for a job doubted that Clauser’s work on Bell’s theorem counted as “real physics.”13
FIGURE 3.1. John Clauser and his contraption to test Bell’s theorem at Berkeley, mid-1970s. (Courtesy Lawrence Berkeley National Laboratory.)
Elizabeth Rauscher paid attention to Clauser’s results. By the early 1970s, Rauscher, a physics graduate student at the Lawrence Berkeley Laboratory, had developed a reputation around the lab somewhat s
imilar to Clauser’s: both enjoyed asking unusual questions. A professor introduced them while Clauser was enmeshed in his first experiment on Bell’s theorem. Soon Rauscher was bringing others over to see Clauser’s makeshift laboratory.14
Rauscher grew up in the Berkeley area. For as long as she can remember, she has been passionate about science. As early as age four she began to study nature. She recalls sitting outside to watch how the grass grows, or gazing up at night, mesmerized by the flickering stars. She loved to get her hands dirty trying to figure things out. She designed, built, and reassembled her own telescopes. Sometimes when she asked her parents questions, they didn’t know the answers. That taught her an important lesson: “people don’t just automatically grow up and know stuff.” Even as a young girl, she realized that she would have to study hard. By the time she reached high school, she began to hang out at the Lawrence Berkeley Laboratory, eager to soak in all the science she could. Back in those days people rarely checked for badges or identification on the lab’s shuttle bus, so she used to board the bus looking as confident as she could, trying to convince the others that she belonged there and knew where she was going. More often than not it worked, and she enjoyed traipsing around the laboratory to see what there was to see.15
How the Hippies Saved Physics: Science, Counterculture, and the Quantum Revival Page 7