12 Experimental …
Does Bell’s discovery show the hidden-variables idea to be worthless? Not at all! What it shows is that any local hidden-variables theory is going to be different from quantum mechanics. Maybe it is quantum mechanics that is worthless. For after all, suddenly we realize that we have not one theory but two: on the one hand quantum mechanics; and on the other hand something else, a hidden-variables picture of the world that does everything that quantum mechanics cannot do and explains the workings of the microworld. It is not a failure to realize that there can be no hidden-variables picture of the world underlying quantum theory. Perhaps it is a wonderful opportunity.
Because if you have two theories, you might want to ask—which one is right? An experiment can decide. An experiment in metaphysics.
John Clauser did the first experiment.
Clauser was born in California. He went to college at Caltech and then to Columbia University for graduate school. It was while he was at Columbia that he had read Bell’s paper announcing his discovery.
It was incredible to me. I didn’t understand it or couldn’t believe it. … I thought “if I don’t believe it, I should be able to give counterexamples” [to prove it wrong]. … So I tried to and failed. I realized: this is the most amazing result I’ve ever seen in my life.1
He had never been happy with quantum theory’s refusal to provide a picture of the physical world:
I am not really a very good abstract mathematician or abstract thinker. Yes, I can conceptualize [quantum theory’s mathematics]. I can work with it, I can sort of know what it is. But I can’t really get intimate with it. I am really very much of a concrete thinker, and I really kind of need a model, or some way of visualizing something in physics.2
Figure 12.1
Clauser later in life. John Clauser performed the first pioneering experiments on Bell’s Theorem. Bell had shown that we have not one but two theories: one is quantum mechanics, and the other is some theory that would fully describe the reality underlying quantum phenomena. Clauser realized that an experiment could be done that would tell us which was correct. His result favored quantum mechanics. Photo courtesy of John Clauser.
Perhaps it was the abstractness of the theory that bothered him. As a matter of fact, all abstractness bothered him:
I had great problems all my life understanding the square root of minus one. In high school, I learned that the square root of minus one was called this little symbol i. Well, there is no such actual number … it’s an imaginary number. If you multiply i times i you get minus one. All right. But suppose I go to the store to buy 1+i candy bars. I could buy one candy bar, or one and a half candy bars, but I couldn’t buy 1+i candy bars. But it’s useful because it makes the equations work out, and once you play with it, the equations work out better that way. So then when I get to [college people would say] “Well, it’s a mathematical artifact. Don’t worry about it. It just makes the equations look nicer.” … I was not very good at it; and didn’t understand, didn’t know why I was doing it. And I felt very uncomfortable with it. And once I felt uncomfortable with it, my brain kind of refused to do it.3
Clauser may have disliked abstraction—but he loved experiments. His father had been an engineer.
As I grew up, basically as a kid, I just would come in after school to his lab. We lived in the suburbs, and so I would do homework—I was supposed to be doing homework, but mostly what I would do is just sort of wander around the lab and gawk at all of the nifty laboratory equipment. And I kept thinking, “Wow, boy do these guys have fun toys. When I grow up I want to be a scientist so that I can play with neat toys like this.”
I was an electronics whiz kid. [My dad] taught me some of the basics of electronics, and I just went off and built some of the earliest computers and the like. I built the world’s first video games, and I actually won a whole bunch of prizes in the National Science Fair for doing this.4
Clauser is enamored of gadgets, and he loves to do experiments. He has lots of patents. One is for a device inspired by something he read in Tom Clancy’s thriller The Hunt for Red October. Another is for a new kind of sail (he is an accomplished yachtsman, with many trophies). Clauser’s garage has done double duty as a laboratory. A bookshelf at home is crammed with catalogs from scientific equipment supply houses. “Anything I need to make, if I don’t have the pieces already, I look for it here. I can make anything.”5 “I’ve gotten pretty good at dumpster diving. … If you are innovative and clever, it’s amazing what you [can do].”6
As for quantum theory, nobody else seemed to share his misgivings about it. “I sat in my corner and tried to understand it myself. Nobody else talked my language.”7 He was alone as he stewed over what he felt to be the theory’s deficiencies.
And the more he stewed, the more Clauser became convinced that quantum theory could not be the whole story. He decided that there had to be hidden variables. And so:
The Vietnam War dominated the political thoughts of my generation. Being a young student living in this era of revolutionary thinking, I naturally wanted to “shake the world.” Since I already believed that hidden variables may indeed exist, I figured that this was obviously the crucial experiment for finally revealing their existence. But if they do exist, then quantum mechanics must be verifiably wrong here, with its error having gone undiscovered heretofore. … To me, the possibility of actually experimentally discovering a flaw in quantum mechanics was mind-boggling.8
So he resolved to do an experiment.
Before he did that experiment, there were a few loose ends to tie up. One was that he needed a different version of Bell’s Theorem. Bell had concerned himself with an ideal situation in which experiments get perfect results. Real experiments, on the other hand, are imperfect. In collaboration with colleagues, Clauser produced a new version of the theorem, one appropriate to such a situation.
I submitted my thesis to Columbia, and I think there was like two weeks or so between submitting the thesis and the thesis defense, which was kind of a dead time. And so I just went up to Boston—actually it was to Wellesley and stayed in [one of my colleague’s] house with him. And [the other colleague] came over pretty much every day, and we just sat there and took two weeks to hash the whole thing out.9
The other loose end was that he had gotten a job across the country, at the University of California at Berkeley. He needed to get from New York to California—and he needed to get his yacht out there too. So he resolved to go by sail.
I had the job out [in California], and I had a boat [in New York City]. And originally, we were just going to sail the boat all the way to Galveston and put it on a truck there, and truck it across to LA and sail it up the coast to Berkeley. It turns out we ran into Hurricane Camille, so we got kind of stopped at Fort Lauderdale. We didn’t save any extra mileage by doing this, but we had a lot of fun sailing down the coast. So every time we put into a port, I would get on the phone and [one of my colleagues] knew my schedule. And so basically he would send off his re-drafts to all of the various marinas in the next city where we put in, some of which I picked up, and some of which are probably still sitting there for all I know. While I was sailing, I would be writing furiously away and editing various things. And we’d get on the phone and chatter about various versions, and we’d keep swapping drafts. This continued all the way until I got to Berkeley, writing the paper, and then we finally submitted it, pretty much right as I arrived in Berkeley.10
If you want to do quantum theory, you need to think about things like the square root of minus one. If you want to do an experiment testing quantum theory, you need to think about things like sandwiches and cardboard.
I had a friend who worked with a particle accelerator. Every time they fired up the machine they needed to pump out all the air within it (you don’t want any air molecules flying around: the particles you are trying to accelerate would bump into them). One day they turned on the vacuum pump and it just couldn’t clear out all the air. It would pump and pump, but the pressure gauge always showed a faint residual pressure. Finally they got tired of waiting. They turned off the pump and opened up the accelerator.
Inside they found a half-eaten ham sandwich. Someone had inadvertently left the thing inside. It had been outgassing, the emitted volatiles spoiling the accelerator’s vacuum. “It was pretty desiccated by the time we got to it,” my friend allowed. “As if it had been freeze-dried.”
Another friend once clapped a sheet of cardboard over the front end of a cutting-edge experiment he was doing—just to keep out the dust. As I recall he also used cardboard to fashion a small, meandering dam around the base of the experiment, to keep out any puddles of water that might form on his laboratory’s floor.
The famous Cosmic Background Radiation, the faint glow left over from the Big Bang, was discovered by two scientists using a gigantic radio telescope. When they got ready to start up the telescope their first project was to get rid of a “milky white dielectric substance” they found coating its surface. The substance turned out to be bird droppings. Another radio astronomer I know used to deal with bird droppings by driving his car right up to his antenna and gently bumping it, to shake the stuff loose.
Clauser built his experiment with the help of a graduate student, Stuart Freedman. The device they built stood maybe waist high and it was about 10 feet long. Inside, an oven heated a chunk of calcium to the vaporization point. Individual atoms streamed out at several thousand miles per hour. They entered a chamber, where they were illuminated by light at a set of precisely calibrated wavelengths. The light induced the atoms to emit a pair of entangled photons (the experiment used photons rather than electrons). These were sent off in opposite directions. Plates of glass formed polarizers—the photon analog of the direction an electron spin detector would point. The photon detectors were immersed in an ultracold slush to improve their performance. Every so often motors would rotate the polarizers to a new configuration, as required by Bell’s Theorem:
At the end of each hundred-second counting cycle, the machine automatically paused and a sequencer (an old telephone relay that Clauser had rescued) would order one or the other polarizer to turn 22.5 degrees in an orchestrated cacophony of domino-like noise and action, vivid in Clauser’s mind thirty years later. “These big mama two-horsepower motors would crank over the “coffins” [holding the polarizers] and the teletype would clatter away,” the paper tape pummeling, accordion-style, into a peach basket, spraying its chads across the floor, to the ka-chunk of the serial printer monitoring the quartz crystal that monitored the calcium beam.11
Two years to build the experiment. Two years of seemingly endless checking and re-checking, of improvising and fiddling and fussing over the details.
An experimenter has to fuss about all sorts of things. You can’t take anything for granted. You have to understand every facet of your experiment. Students often don’t understand this: they want to charge ahead, throw the apparatus together, turn it on and get a result. Their instructors can have a hard time of it slowing them down.
Clauser:
People always think you don’t have the time to test everything. … The truth is you don’t not have the time. It’s actually the time-saving way of doing it. It’s hard, when you’re eager to know what Nature’s doing: you almost have to train yourself to be anticurious while you’re building your hardware. People always want to slap it all together, turn it on, and see what happens. But for the first run, you can almost guarantee it’s not going to work right.12
If you don’t like this sort of thing, you don’t want to become an experimentalist. Many people don’t—me, for instance. Others do. I was chatting with a friend recently about the whole business of getting an experiment up and running. He was talking about how careful he had to be, how many errors there were to be chased down, and how slow was the progress. At one point he leaned back, gazed at the ceiling, and mused. “There are so many things in an experiment to worry over,” he said. “So much to get under control. It is really—”
Before my friend finished speaking, I thought I knew what he was going to say. In my mind I finished his sentence for him. In my mind I had him saying something like “a royal pain in the ass.” But, as it turned out, that was not what he said.
“Fascinating” was what he said. And he smiled again.
Clauser kept slogging. Throughout it all, he had finally found other people interested in his favorite topic, the mysteries of quantum mechanics. This was a wild and woolly group of physicist-hippies—it was, after all, the age of the counterculture and the antiwar movement—that called itself the Fundamental Fysiks Group. Its members would meet every Friday afternoon around a table at the University of California at Berkeley. There they engaged in a wide-ranging, free-form discussion of a breathtakingly wide variety of subjects. Topics ranged from the significance of Bell’s Theorem to faster-than-light communication, from ESP to LSD.
Clauser joined the group—sort of: “Those guys were a bunch of nuts, really. … But we kind of used that as a forum. The real physicists were over here in one corner, and all the kooks are in the other corner.”13 There were meetings at the Esalen Institute in Big Sur:
The guy who was running this decided that quantum mechanics was related to this consciousness expansion, and would bring us down there. It was free for us, and there were hot sulfur baths that were there, and the rocks, and you’d go into these hot baths, all communal, with everybody naked, which I guess was part of the grand excitement. And then the hot water would sort of overflow the tubs and go cascading down the cliff into the Pacific Ocean. And so part of the highlight of every evening was a trip to the baths. And then during the day, we would sit around and talk about new aspects of quantum mechanics and the like, and how it was related to the great cosmic cockroach, or whatever. None of which I thought very much of, but what the heck?14
Eventually, Clauser and Freedman got their machine up and running. Once built, it ran for a total of two hundred hours spaced over several months. They got a result.
Their result disagreed with the local hidden-variables hypothesis, and it supported quantum mechanics.
Clauser’s pioneering experiment had been conducted in the face of the scorn and antipathy of which I wrote in the previous chapter. And Clauser paid a price. Many colleagues felt little interest in his work, showed little interest in its results, and felt free to advise others of their opinion. He never got a position at a university or college—this in spite of glowing recommendations from prestigious senior colleagues. “I believe he shows promise of becoming one of the most important experimentalists of the next decade,” wrote one. But it was to no avail: over the decades following on his experiment Clauser was forced to work in a research laboratory or on his own as an entrepreneur.
In 2002 Clauser wrote about his early experiences. His article rings with irritation at the reception his work had received:
Most of the [subject] represented forbidden thinking for practicing physicists. Indeed, any open inquiry into the wonders and peculiarities of quantum mechanics … was then virtually prohibited by the existence of various religious stigmas and social pressures, that taken together, amounted to an evangelical crusade against such thinking.15
Later on in his article Clauser writes of McCarthyism and relates it to
a very powerful secondary stigma [that] began to develop within the physics community towards anybody who sacrilegiously was critical of quantum theory’s fundamentals. … The net impact of this stigma was that any physicist who openly criticized or even seriously questioned these foundations (or predictions) was immediately branded as a “quack.”16
In the long run, Clauser’s work has been widely recognized as a pioneering triumph—he received a prestigious award for it in 2010. But the long run was far off in the future while he was doing his experiment.
A quick aside.
It was when he was a graduate student at Columbia University in New York (working on a PhD thesis involving astrophysics) that Clauser became captivated by Bell’s Theorem. It turns out that he and I are pretty much the same age—and I was working at a research institute just a few blocks down the street from Columbia. I remember meeting him. We did not get to know each other well. It was a matter of just a few encounters. But even now, decades after these encounters, memories stand out in my mind.
One was that Clauser lived, not in an apartment like everybody else in New York, but on a yacht—a yacht of his own, which he moored in some marina nearby. (Recall that, on finishing up at Columbia he had set out to sail all the way to California. He is a serious yachtsman.) Unusual enough. Another was that all he wanted to talk about was Bell’s Theorem.
And there’s one other memory. I recall what I said to him. “Bell’s Theorem? Never heard of it. What is it?”
There’s that stigma again. I was infected too.
Clauser’s experiment had shot down the hidden variable idea … nearly. Quantum theory was vindicated … nearly. Unfortunately, however, there was a loophole—a loophole through which the hidden variable concept might just possibly manage to squeeze.
An analogy to Clauser’s experiment is a variation of my angry couple, intent on disagreeing with one another. To make it vivid, imagine that they live in Kansas. One day, furious and irritable, they separate. The wife heads off to Oregon. When she arrives she encounters an individual (named Alice) who for some reason is full of questions. The questions keep changing. “Do you like steak?” Alice might ask. Or alternatively “do you like fish?” or “do you like exercise?” Meanwhile, the husband has just arrived in Florida, where he is bombarded with questions by Bob—questions that are sometimes the same, but sometimes different, than those asked by Alice. “Do you like steak?” might well be the first of Bob’s questions—but it also might be “do you like fish?”
As before, the husband and wife are intent on disagreeing with each other (not always now, but by a certain definite amount). The problem is that they don’t know how to do it. After all, neither one of them knows the reply the other has given. They don’t even know what question the other has answered! So how can they synchronize their replies?
Here’s a way. They can phone one another.
That is the loophole. If husband and wife could tell each other what the questions had been, and what their replies had been, they could synchronize those replies. Some sort of “telephone connection” between them would accomplish this. There is nothing in all of physics that explains just how this connection might work. Of course it’s not a matter of actual phone calls from one quantum particle to another: there’s no such thing. It would have to be something else: something that has never been thought of before. But so what? Maybe it’s possible after all.
That loophole is a vulnerability in Clauser’s experiment. So his conclusion was open to attack. Perhaps quantum mechanics was not the right theory after all. Perhaps hidden variables actually did exist.
But several years after Clauser’s experiment, a French physicist named Alain Aspect found a way to close that loophole. He did this by blocking the phone calls. He rendered those telephones—if they existed at all—irrelevant.
Remarkably Aspect managed to do this even though he knew very little about how those hypothetical phones might possibly work. Of course, that’s a hard job. Normally, in order to defend against an attack, you had better know something about the nature of that attack. How can you defend against an unknown enemy?
Aspect took advantage of the fact that he did know one little thing about that enemy: it could not travel faster than light. The signals from one quantum particle to the other, whatever they might possibly be, had to obey that cosmic speed limit.
Figure 12.2
Alain Aspect. Clauser’s experiment had a potential loophole: that somehow the two entangled particles could communicate with one another. Aspect closed that loophole by randomly changing the “questions” asked of them.
The principle that no signal can travel faster than light is enshrined in physics. It has been experimentally tested over and over again, and always found valid. Not even the weird quantum world can violate it. Aspect found a way to use this principle in his experiment. He created a situation in which the husband and wife would set forth on their journeys, one to Oregon and one to Florida—perhaps carrying telephones of some unknown design, and perhaps talking with one another as they traveled. But because those phone signals were not traveling with infinite velocity—the speed of light is great, but not infinite—there would be a tiny interval of time the transmissions took to travel between husband and wife. And in that tiny interval, Alice and Bob would change their questions.
In such a situation, the husband and wife would find themselves forced to answer a question before they could exchange information. Even had they possessed telephones, the transmissions would arrive too late. As a consequence, each reply would be given in a state of total ignorance. Aspect would have rendered those hypothetical telephones irrelevant.
He built the experiment. Then he ran it. He found that the new twist made no difference. His data showed that, astonishingly, husband and wife still managed to synchronize their responses. They disagreed more often than could be accounted for. They persisted in doing the impossible.
I will say it again: they were doing something for which there is no possible explanation.
So Aspect closed the loophole. Unfortunately, however, there is not just one loophole. There are many.
Here’s another—and this is one that was closed by one of the prettiest experiments I have seen in years. It is known as the “freedom of choice loophole” and it proposes that Alice and Bob may think they have free will … but actually they don’t.
What does freedom of choice have to do with hidden variables? In chapter 9’s discussion of a hidden-variable theory, I showed that if Bob rotates his analyzer, a certain fraction of the detections will show disagreements with Alice’s result. But quantum theory predicts more disagreements than that, and Clauser’s experiment confirmed the quantum prediction. In chapter 9, I tried to alter the hidden-variable theory by having the source avoid emitting particles in a certain direction (into the wedge of figure 9.6) in order to mimic quantum theory. But, as I wrote, this attempt at a fix would not work since Alice and Bob have freedom of choice. They are free to act in any way they wish. They might elect to turn their analyzers not to the right but to the left—or not by this angle but by that. Since there is no way to adjust the source in advance to deal with every possible choice, the conclusion was that the hidden-variable idea is not going to work.
But maybe that conclusion is not so certain. For suppose that Alice and Bob are not really free to turn their analyzers in just any old which way. Suppose their much-vaunted free will is actually an illusion. Suppose that yesterday they had been hypnotized, and today they are under the sway of a posthypnotic suggestion forcing them to swing their analyzers only in certain ways … and suppose that the source knows about these ways.
I’m speaking metaphorically, of course. In real experiments sources don’t “know” anything. And the analyzers’ orientations are not chosen by people: they are chosen by machines, components of the experimental apparatus. Experimenters try to make sure that these machines behave randomly. But what if they are not fully successful? What if their so-called “random machines” are not really random? What if those machines are actually being controlled by some process of which the experimenters are entirely unaware—a process that connects both the source and the analyzers, and that deceives us into believing in quantum mechanics?
Just like Aspect’s “phone calls,” there is nothing in all of physics that tells us which this controlling process might be. But, again like Aspect’s situation—so what? Maybe it is possible after all. That would be a loophole too.
The freedom of choice experiment did not entirely close this loophole. But it did restrict it—dramatically. It showed that this hypothetical controlling influence must not operate in the here and now. Rather it operated centuries ago, and it came from a location thousands of trillions of miles away. The experiment grabbed hold of that control, and it shoved it far off into the depths of time and cosmos.
Anton Zeilinger, a burly, affable man with an infectious sense of humor and a love of life, is a worldwide leader in work on quantum entanglement. Throughout his career he has conducted numerous groundbreaking experiments probing the many astonishments of quantum mechanics. In Zeilinger’s lab in downtown Vienna, a source emitted entangled pairs of particles. (Like Aspect’s, the actual experiment worked with photons instead of electrons, and it measured their polarizations instead of spins.) A third of a mile away was a bank. We can call it “Alice’s bank” if we wish. One evening a group of physicists invaded that bank. But they were not there to steal. Rather, they were there to assemble two sets of scientific equipment, peering out of two different windows.
One of those windows had a good view of Zeilinger’s lab. Through the window peered a device capable of revealing the polarization of an incoming photon, a photon shot out from his lab. Out a different window, one facing in the opposite direction, peered a telescope. It was peering, not at a lab, not even at any earthbound building, but up into the sky. It was gazing at a star.
Figure 12.3
Anton Zeilinger. Clauser’s experiment had another potential loophole: that the “questions” asked of the two particles only seemed random, but were in fact being dictated by some unknown mechanism. Zeilinger’s experiment showed that this mechanism, if it existed at all, lay far off in the universe and operated far back in the past. Photo courtesy of the Mind & Life Institute, © The Mind & Life Institute.
That telescope was not one of those mighty instruments so beloved of astronomers, perched on mountaintops or orbiting the earth, but rather the sort of small, unassuming device that an amateur astronomer might own. Indeed, the telescope was not the hard part of the experiment. The hard part was what it was connected to—and this was the sort of stuff no amateur could afford. Part of that stuff was an instrument that observed individual photons of the light from the star. At any instant a star—or any other source of light—is emitting a vast flood of photons, all of different colors. The experiment’s equipment was set to grab those photons one by one … and measure the color of each. Was it more nearly red, or more nearly blue?
Information about that color was routed across the bank to the analyzer trained on Zeilinger’s lab. And there it entered the most extraordinary of devices: a device that set the orientation of that analyzer according to the information from the telescope—and that was capable of changing its orientation in a millionth of a second. And that was the key element of the experiment: the orientation of the analyzer was set by the color of the starlight.
All this equipment peering out of the windows in the bank constituted our “Alice.” As for “Bob,” he was located in a different building—a mile away, on the far side of Zeilinger’s lab and its source of entangled photons. In Bob’s building stood similar equipment, with the analyzer catching the second member of the entangled pair, and with the telescope pointing to a second star, whose photon would determine the orientation of Bob’s analyzer.
In this way, the group had devised a setup in which the choice of orientations of the analyzers—the questions to ask of the husband and wife—was determined not by the choice of the experimenters, not by the action of some piece of equipment situated in the lab, but rather by infinitesimal bits of light from two different stars as they twinkled in the evening sky over Vienna.
They ran the experiment. It got results in agreement with quantum theory and opposed to the hidden-variable theory.
If we are talking about a loophole involving free will, the “will” we are talking about is that of those two stars. It was they that were directing the experiment, directing by means of photons launched centuries ago. One of the stars was 600 light years away, which amounts to thousands of trillions of miles. And the light it emitted had been sent forth on its journey toward Vienna 600 years in the past. The other star was more distant still.
Could our hypothetical “preordaining influence”—our hypnotist—have intervened in the experiment to invalidate its results? It could have done so only by controlling those bits of starlight. That is to say, only by intervening not in Vienna, but far off in the Milky Way. And it was not even intervening now: it had done so centuries ago … at a time, in the words of one of those experimenters, “back when Joan of Arc’s friends still called her Joanie.”17
And just like Aspect with his experiment, the freedom of choice group found that their new twist made no difference. Their data showed that, astonishingly, husband and wife still managed to synchronize their responses. They disagreed more often than could be accounted for. They persisted in doing the impossible.
Not too many years ago a graduate student had a wonderful idea. He decided to invent a game. A metaphysical game.
The student’s name was Carlos Abellán. He worked in a research group led by Morgan Mitchell, based in Barcelona. For years the two of them had been batting around the whole idea of randomness.
Figure 12.4
Carlos Abellán (left) and Morgan Mitchell (right). Photo: ICFO.
Are the “questions” asked of the two particles really random? All previous experiments had relied on some physical mechanism to achieve randomness—but mechanisms obey the laws of classical physics, and so are not truly random. In the “the BIG Bell Test experiment” vast numbers of people were enlisted to use their free will to create randomness.
Figure 12.5
The app they created. Image: Maria Pascual (Kaitos Games).
Randomness is a key element of any experiment aiming to test Bell’s Theorem. It is the only way to ensure that our angry couple, intent on disagreeing with one another, have no way of knowing the questions they are about to be asked. And up to that point all the various Bell-test experiments had achieved this randomness by mechanical means. They used marvelous and elaborate mechanisms that were designed to behave unpredictably as they dictated the orientation of the analyzers. Even the distant stars in the experiment I have just described were at heart mechanisms—the fact they were natural rather than artificial was irrelevant. But Abellán and Mitchell found themselves wondering: are any mechanisms truly random? Or do they only seem to be?
My smartphone tells me that apps exist that behave randomly. Indeed, I can buy chance. Just now I checked the App Store, and there I found all sorts of random-number generators. I could download any one of them: each time I asked, it would give me some unpredictable number.
But are these numbers really unpredictable? No, they are not. We tend to forget that all the marvelous stuff we find on the Web rests in the last analysis on actual, physical machines. We say that those random-number generators reside “in cyberspace”—but cyberspace is not a real thing. It is a term we use for radio signals traveling this way and that through an elaborate network connecting our smartphones with servers—and each of these servers is a computer, an actual, physical device composed of actual physical parts. Somewhere, deep in the guts of a rack of electronics in some faraway server farm, tiny electrical currents flow this way instead of that, and tiny magnets are orientated one way instead of another … and the working of this immense collection of electromagnetic parts is the working of cyberspace. If I knew exactly the physical configuration of that server I would find that my vaunted random-number generator was only an apparently random-number generator.
Maybe this will become more evident if we consider the act of flipping a coin. It is the quintessential example of randomness. Can I predict how that coin will land? Of course not. But is it random? No, it is not.
Suppose I knew exactly how high I had tossed that coin. Then I would be able to predict how long it would take before landing. And suppose I knew exactly how much spin my thumb had imparted to it. Then I would know how rapidly it was rotating during its flight, and how many times it had spun over in that interval of time. And if I knew how hard it landed, and at what angle it had struck the table when it did so, then I could predict how high it would bounce and how many times it would flip over before finally coming to rest. And if I knew whether that coin was showing heads or tails just before I flipped it … why then, if I knew all these things, I would have been able to predict what that flipped coin would show when it landed. And make a million dollars.
For in truth, a flipped coin does not exhibit randomness. Neither does my so-called random-number generator. What they exhibit is complexity.
You might be objecting that my “research projects” into the flight of the coin or the workings of my app are not something that I could carry out in practice. I agree—but so what? We are not speaking of “in practice.” We are speaking of “in principle,” and the principle is one of absolute determinism: everything that happens in the large-scale world is dictated by the inflexible law of cause and effect. And if it is dictated then it is in principle foreseeable … and in that case what our mythical angry couple is doing may not be so very mysterious after all.
That’s another loophole.
Abellán and Mitchell wanted to nail that loophole shut. They wanted to achieve something no machine could do, and achieve true randomness. They asked themselves: what were the most erratic things in the universe?
People were, they decided.
You and me. The butcher and the baker and the candlestick maker and everybody else too. All of humanity, in the messiness and unpredictability of free will. Never mind those coin-flips and servers and distant stars: Abellán and Mitchell would assemble a team to build an experiment in which it was not a physical mechanism that chose how to rotate the analyzers to and fro. It would be people—ordinary people, people from every walk of life—who made those random choices.
It was not a new idea. Many researchers had already bandied about the notion of replacing machines with humans. But nobody could figure out how to make it work. The problem was that people were not fast enough. They were capable of making choices only so often—a few times per second, maybe. But the experiments needed to flip their analyzers’ orientations at lightening speeds.
Abellán’s wonderful idea was to circumvent this limitation by using large numbers of people. How to get in touch with them? Use social media. And how to persuade them to make those random choices? Lure them in. Invent something so attractive, so seductive and enticing, that vast numbers of people would be sucked into the project. How to do this? By inventing a game.
It would be an online game. The researchers would create a network of players, a vast agglomeration encompassing huge numbers of people from across the globe, all playing the game at the very same time and each one of them making random choices. Out of this network of players an immense storehouse of pure chance would accumulate. Accumulate, and drive the course of experiments testing Bell’s Theorem.
They called their game “the BIG Bell Test.” It lived on a website.a
The test would ask people to make choices. It was actually very simple, if truth be told: all a player had to do was enter a series of 0’s and 1’s into a smartphone. The hard part was that this had to be done randomly and rapidly.
The experimenters built into their app all the elements of modern gaming: trendy animations and sound effects to cheer the gamers on their way, leaderboards, boss battles and power-ups, the opportunity to form groups and compare their skill levels with those of fellow-gamers. From time to time players would be reminded that their inputs were being used in actual experiments underway at that very moment in laboratories across the globe. And as they refined their skills and graduated from one level of the game to the next, they might be rewarded with some interesting tidbit about the mathematics of randomness, or by a prerecorded video from one of the experiments.
Meanwhile the Oracle would be watching.
The Oracle’s function was to tell the players how well they were doing—how much randomness they were achieving. For it turns out that it is not so easy to be random. Suppose for instance that, as you madly typed away, you just happened to enter three 0’s in a row. Studies have shown that in such a situation you are more likely to avoid 0 for your fourth step and enter a 1 instead. This in spite of the fact that true randomness dictates that you should be equally likely to choose either. The Oracle was a “prediction engine” that studied your previous entries and tried to anticipate your next: if it succeeded, this was proof that you were not achieving true randomness. And the Oracle would tell you so. The Oracle was the enemy against which you were competing.
Having built their game, the next step was to recruit the players. (They called them “Bellsters.”) A massive advertising campaign was launched—on social media, in newspapers and TV ads and announcements to schools and science museums. More than 230 headlines resulted. The game and accompanying information were made available on the group’s website in seven languages, making it accessible to over three billion people: that is nearly half the world’s population.
Of course, all this was only the first step. What about the experiments that would use the data? The members of Mitchell’s group were planning to run their own experiment. But they wanted others. They advertised their project to laboratories across the world, and ultimately assembled a group of researchers running fully 13 different experiments. They were situated in nations spanning the globe: Barcelona, China, the United States …
Everything would happen at the same time: experiments running, Bellsters gaming. The whole thing was a massive exercise in organization. Gaming day was set for November 30, 2016.
Across the spinning globe daylight dawned. The experiments fired up and got ready for the data. Meanwhile, the gamers got busy. They came from most of the nations of the world: from Europe and the Americas, from China, Australia—there were even some from Antarctica. Over the course of the next 51 hours some 100,000 gamers entered their data: more than 97 million 0’s and 1’s. Over one 12-hour period the worldwide group reached and sustained a rate of 1,000 random choices per second.
The 13 experiments, all running at the same time, used these data to test Bell’s Theorem. Every one of them found that quantum mechanics was valid and hidden variables were not.
It all rests on a conundrum, of course. For is it really true that we have free will? Were the gamers actually behaving randomly? I think it is fair to say that our brains are machines. and so cannot be truly random. But a brain—the actual, physical object lying between our ears—is one thing, and a mind is another. Is it possible for our brains to be deterministic while at the same time we humans are not? As for myself, I have no idea.
So we can make of this project what we will. Perhaps it adds a vital element to the situation and perhaps not. But no matter: it was a wonderful project—wonderful for the gamers and, I am willing to bet, for the scientists too.
Nowadays many groups of experimentalists are hard at work, closing loophole after loophole. There are certainly enough of them to be closed. Why only last week I came across an article listing fully ten. The task of closing all these loopholes is not yet complete. Indeed, it is not even a matter of closing first one and then another: best of all would be to close them all at once. So it’s a slow process.
But perhaps you feel that all this effort is just a little bit silly. After all—aren’t these physicists being maybe just a little bit paranoid? Are they perhaps starting to resemble some bunch of conspiracy theorists, hard at work inventing one nutty idea after another? Who could possibly take seriously the notions of “phone calls between particles” or “preordaining influences”—notions without the slightest thing to recommend them beyond my lame assertion that “maybe it is possible after all”?
I’ll tell you who would do all this: anybody who wants to be sure about quantum theory—very sure, as sure as humanly possible about one of the most important scientific discoveries of all time.
Scientists want their knowledge to be trustworthy. All of us want our knowledge to be trustworthy. So much of life is uncertain. We want as much certainty as we can get. We want to be able to trust what little we do know.
I like to think in terms of the analogy of climbing a ladder. Suppose you have propped a ladder up against a wall—a long ladder, one that will carry you way up into the heights. Would you be willing to start up that ladder before making sure it is secure? As for me, I certainly wouldn’t. I would shake it, swing it to and fro.
In doing so, my goal is not to knock the ladder down. It is to make sure that nothing else can knock it down. That’s what these loophole-chasers are doing. They are “shaking” quantum mechanics in every way they can. They are probing for weaknesses in all the various experiments that purport to confirm the theory—all in order to make sure that the experiments are trustworthy. And the results to date have shown that the ladder that is quantum mechanics is utterly trustworthy.
But I would not want to leave it at that. For in truth I believe that there is a further reason these people are spending so much time and effort on all these beautiful experiments. It is that the experiments really are beautiful. It is that only now, now that the latest and sexiest gadget is available from that high-tech corporation in Texas; and only now that those colleagues down the hall have invented yet another brilliant technique for doing yet another new thing—only now has it suddenly become possible to do what yesterday was impossible. So you get down to cases and you do do it.
I love that about science: that great, windblown sense of openness about the whole enterprise.
a. You can play this game yourself. See https://
Notes