by Dan Ariely
Deutsch believes that quantum computing and Many Worlds are inextricably bound. He is nearly alone in this conviction, though many (especially around Oxford) concede that the construction of a sizable and stable quantum computer might be evidence in favor of the Everett interpretation. “Once there are actual quantum computers,” Deutsch said to me, “and a journalist can go to the actual labs and ask how does that actual machine work, the physicists in question will then either talk some obfuscatory nonsense or will explain it in terms of parallel universes. Which will be newsworthy. Many Worlds will then become part of our culture. Really, it has nothing to do with making the computers. But psychologically it has everything to do with making them.”
It’s tempting to view Deutsch as a visionary in his devotion to the Many Worlds Interpretation, for the simple reason that he has been a visionary before. “Quantum computers should have been invented in the nineteen-thirties,” he observed near the end of our conversation. “The stuff that I did in the late nineteen-seventies and early nineteen-eighties didn’t use any innovation that hadn’t been known in the thirties.” That is straightforwardly true. Deutsch went on, “The question is why.”
DiVincenzo offered a possible explanation. “Your average physicists will say, ‘I’m not strong in philosophy and I don’t really know what to think, and it doesn’t matter.’” He does not subscribe to Many Worlds but is reluctant to dismiss Deutsch’s belief in it, partly because it has led Deutsch to come up with his important theories, but also because “quantum mechanics does have a unique place in physics, in that it does have a subcurrent of philosophy you don’t find even in Newton’s laws of gravity. But the majority of physicists say it’s a quagmire they don’t want to get into—they’d rather work out the implications of ideas; they’d rather calculate something.”
At Yale, a team led by Robert Schoelkopf has built a two-qubit quantum computer. “Deutsch is an original thinker, and those early papers remain very important,” Schoelkopf told me. “But what we’re doing here is trying to develop hardware, to see if these descriptions that theorists have come up with work.” They have configured their computer to run what is known as a Grover’s algorithm, one that deals with a four-card-monte type of question: Which hidden card is the queen? It’s a sort of Shor’s algorithm for beginners, something that a small quantum computer can take on.
The Yale team fabricates their qubit processor chips in house. “The chip is basically made of a very thin wafer of sapphire or silicon—something that’s a good insulator—that we then lay a patterned film of superconducting metal on to form the wiring and qubits,” Schoelkopf said. What they showed me was smaller than a pinkie nail and looked like a map of a subway system.
Schoelkopf and his colleague Michel Devoret, who leads a separate team, took me to a large room of black lab benches, inscrutable equipment, and not particularly fancy monitors. The aesthetic was inadvertent steampunk. The dust in the room made me sneeze. “We don’t like the janitors to come sweep for fear they’ll disturb something,” Schoelkopf said.
The qubit chip is small, but its supporting apparatus is imposing. The largest piece of equipment is the plumbing of the very high-end refrigerator, which reduces the temperature around the two qubits to 10 millidegrees above absolute zero. The cold improves the computer’s fidelity. Another apparatus produces the microwave signals that manipulate the qubits and set them into any degree of superposition that an experimenter chooses.
Running this Grover’s algorithm takes a regular computer three or fewer steps—if, after checking the third card, you still haven’t found the queen, you know she is under the fourth card—and on average it takes 2.25 steps. A quantum computer can run it in just one step. This is because the qubits can represent different values at the same time. In the four-card-monte example, each of the cards is represented by one of four states: 0,0; 0,1; 1,0; 1,1. Schoelkopf designates one of these states as the queen, and the quantum computer must determine which one. “The magic comes from the initial state of the computer,” he explained. Both of the qubits are set up, via pulses of microwave radiation, in a superposition of zero and one, so that each qubit represents two states at once, and together the two qubits represent all four states.
“Information can, in a way, be holographically represented across the whole computer; that’s what we exploit,” Devoret explained. “This is a property you don’t find in a classical information processor. A bit has to be in one state—it has to be here or there. It’s useful to have the bit be everywhere.”
Through superposition and entanglement, the computer simultaneously investigates each of the four possible queen locations. “Right now we only get the right answer eighty percent of the time, and we find even that pretty exciting,” Schoelkopf said.
With Grover’s algorithm, or theoretically with Shor’s, calculations are performed in parallel, though not necessarily in parallel worlds. “It’s as if I had a gazillion classical computers that were all testing different prime factors at the same time,” Schoelkopf summarized. “You start with a well-defined state, and you end with a well-defined state. In between, it’s a crazy entangled state, but that’s fine.”
Schoelkopf emphasized that quantum mechanics is a funny system but that it really is correct. “These oddnesses, like superposition and entanglement—they seemed like limitations, but in fact they are exploitable resources. Quantum mechanics is no longer a new or surprising theory that should strike us as odd.”
Schoelkopf seemed to suggest that existential questions like those that Many Worlds poses might be, finally, simply impracticable. “If you have to describe a result in my lab in terms of the computing chip,” he continued, “plus the measuring apparatus, plus the computer doing data collection, plus the experimenter at the bench . . . at some point you just have to give up and say, Now quantum mechanics doesn’t matter anymore, now I just need a classical result. At some point you have to simplify, you have to throw out some of the quantum information.” When I asked him what he thought of Many Worlds and of “collapse” interpretations—in which “looking” provokes a shift from an entangled to an unentangled state—he said, “I have an alternate language which I prefer in describing quantum mechanics, which is that it should really be called Collapse of the Physicist.” He knows it’s a charming formulation, but he does mean something substantive in saying it. “In reality it’s about where to collapse the discussion of the problem.”
I thought Deutsch might be excited by the Yale team’s research, and I e-mailed him about the progress in building quantum computers. “Oh, I’m sure they’ll be useful in all sorts of ways,” he replied. “I’m really just a spectator, though, in experimental physics.”
Sir Arthur Conan Doyle never liked detective stories that built their drama by deploying clues over time. Conan Doyle wanted to write stories in which all the ingredients for solving the crime were there from the beginning, and in which the drama would be, as in the Poe stories that he cited as precedents, in the mental workings of his ideal ratiocinator. The story of quantum computing follows a Holmesian arc, since all the clues for devising a quantum computer have been there essentially since the discovery of quantum mechanics, waiting for a mind to properly decode them.
But writers of detective stories have not always been able to hew to the rationality of their idealized creations. Conan Doyle believed in “spiritualism” and in fairies, even as the most famed spiritualists and fairy photographers kept revealing themselves to be fakes. Conan Doyle was also convinced that his friend Harry Houdini had supernatural powers; Houdini could do nothing to persuade him otherwise. Conan Doyle just knew that there was a spirit world out there, and he spent the last decades of his life corralling evidence ex post facto to support his unshakable belief.
Physicists are ontological detectives. We think of scientists as wholly rational, open to all possible arguments. But to begin with a conviction and then to use one’s intellectual prowess to establish support for that conviction
is a methodology that really has worked for scientists, including Deutsch. One could argue that he dreamed up quantum computing because he was devoted to the idea that science can explain the world. Deutsch would disagree.
In The Fabric of Reality, Deutsch writes, “I remember being told, when I was a small child, that in ancient times it was still possible to know everything that was known. I was also told that nowadays so much is known that no one could conceivably learn more than a tiny fraction of it, even in a long lifetime. The latter proposition surprised and disappointed me. In fact, I refused to believe it.” Deutsch’s life’s work has been an attempt to support that intuitive disbelief—a gathering of argument for a conviction he held because he just knew.
Deutsch is adept at dodging questions about where he gets his ideas. He joked to me that they came from going to parties, though I had the sense that it had been years since he’d been to one. He said, “I don’t like the style of science reporting that goes over that kind of thing. It’s misleading. So Brahms lived on black coffee and forced himself to write a certain number of lines of music a day. Look,” he went on, “I can’t stop you from writing an article about a weird English guy who thinks there are parallel universes. But I think that style of thinking is kind of a putdown to the reader. It’s almost like saying, If you’re not weird in these ways, you’ve got no hope as a creative thinker. That’s not true. The weirdness is only superficial.”
Talking to Deutsch can feel like a case study of reason following desire; the desire is to be a creature of pure reason. As he said in praise of Freud, “He did a good service to the world. He made it OK to speak about the mechanisms of the mind, some of which we may not be aware of. His actual theory was all false, there’s hardly a single true thing he said, but that’s not so bad. He was a pioneer, one of the first who tried to think about things rationally.”
JOSHUA DAVIS
The Crypto-Currency
FROM The New Yorker
THERE ARE LOTS of ways to make money: you can earn it, find it, counterfeit it, steal it. Or, if you’re Satoshi Nakamoto, a preternaturally talented computer coder, you can invent it. That’s what he did on the evening of January 3, 2009, when he pressed a button on his keyboard and created a new currency called bitcoin. It was all bit and no coin. There was no paper, copper, or silver—just 31,000 lines of code and an announcement on the Internet.
Nakamoto, who claimed to be a thirty-six-year-old Japanese man, said he had spent more than a year writing the software, driven in part by anger over the recent financial crisis. He wanted to create a currency that was impervious to unpredictable monetary policies as well as to the predations of bankers and politicians. Nakamoto’s invention was controlled entirely by software, which would release a total of 21 million bitcoins, almost all of them over the next twenty years. Every ten minutes or so, coins would be distributed through a process that resembled a lottery. Miners—people seeking the coins—would play the lottery again and again; the fastest computer would win the most money.
Interest in Nakamoto’s invention built steadily. More and more people dedicated their computers to the lottery, and forty-four exchanges popped up, allowing anyone with bitcoins to trade them for official currencies like dollars or euros. Creative computer engineers could mine for bitcoins; anyone could buy them. At first a single bitcoin was valued at less than a penny. But merchants gradually began to accept bitcoins, and at the end of 2010 their value began to appreciate rapidly. By June 2011, a bitcoin was worth more than $29. Market gyrations followed, and by September the exchange rate had fallen to $5. Still, with more than 7 million bitcoins in circulation, Nakamoto had created $35 million of value.
And yet Nakamoto himself was a cipher. Before the debut of bitcoin, there was no record of any coder with that name. He used an e-mail address and web site that were untraceable. In 2009 and 2010, he wrote hundreds of posts in flawless English, and though he invited other software developers to help him improve the code, and corresponded with them, he never revealed a personal detail. Then in April 2011, he sent a note to a developer saying that he had “moved on to other things.” He has not been heard from since.
When Nakamoto disappeared, hundreds of people posted theories about his identity and whereabouts. Some wanted to know if he could be trusted. Might he have created the currency in order to hoard coins and cash out? “We can effectively think of ‘Satoshi Nakamoto’ as being on top of a Ponzi scheme,” George Ou, a blogger and technology commentator, wrote.
It appeared, though, that Nakamoto was motivated by politics, not crime. He had introduced the currency just a few months after the collapse of the global banking sector, and he published a five-hundred-word essay about traditional fiat, or government-backed, currencies. “The root problem with conventional currency is all the trust that’s required to make it work,” he wrote. “The central bank must be trusted not to debase the currency, but the history of fiat currencies is full of breaches of that trust. Banks must be trusted to hold our money and transfer it electronically, but they lend it out in waves of credit bubbles with barely a fraction in reserve.”
Banks, however, do much more than lend money to overzealous homebuyers. They also, for example, monitor payments so that no one can spend the same dollar twice. Cash is immune to this problem: you can’t give two people the same bill. But with digital currency there is the danger that someone can spend the same money any number of times.
Nakamoto solved this problem using innovative cryptography. The bitcoin software encrypts each transaction—the sender and the receiver are identified only by a string of numbers—but a public record of every coin’s movement is published across the entire network. Buyers and sellers remain anonymous, but everyone can see that a coin has moved from A to B, and Nakamoto’s code can prevent A from spending the coin a second time.
Nakamoto’s software would allow people to send money directly to each other without an intermediary, and no outside party could create more bitcoins. Central banks and governments played no role. If Nakamoto ran the world, he would have just fired Ben Bernanke, closed the European Central Bank, and shut down Western Union. “Everything is based on crypto proof instead of trust,” Nakamoto wrote in his 2009 essay.
Bitcoin, however, was doomed if the code was unreliable. Earlier this year, Dan Kaminsky, a leading Internet security researcher, investigated the currency and was sure he would find major weaknesses. Kaminsky is famous among hackers for discovering, in 2008, a fundamental flaw in the Internet that would have allowed a skilled coder to take over any web site or even to shut down the Internet. Kaminsky alerted the Department of Homeland Security and executives at Microsoft and Cisco to the problem and worked with them to patch it. He is one of the most adept practitioners of “penetration testing,” the art of compromising the security of computer systems at the behest of owners who want to know their vulnerabilities. Bitcoin, he felt, was an easy target.
“When I first looked at the code, I was sure I was going to be able to break it,” Kaminsky said, noting that the programming style was dense and inscrutable. “The way the whole thing was formatted was insane. Only the most paranoid, painstaking coder in the world could avoid making mistakes.”
Kaminsky lives in Seattle, but while visiting family in San Francisco in July, he retreated to the basement of his mother’s house to work on his bitcoin attacks. In a windowless room jammed with computers, Kaminsky paced around talking to himself, trying to build a mental picture of the bitcoin network. He quickly identified nine ways to compromise the system and scoured Nakamoto’s code for an insertion point for his first attack. But when he found the right spot, there was a message waiting for him. “Attack Removed,” it said. The same thing happened over and over, infuriating Kaminsky. “I came up with beautiful bugs,” he said. “But every time I went after the code there was a line that addressed the problem.”
He was like a burglar who was certain that he could break into a bank by digging a tunnel, drilling through a wa
ll, or climbing down a vent, and on each attempt he discovered a freshly poured cement barrier with a sign telling him to go home. “I’ve never seen anything like it,” Kaminsky said, still in awe.
Kaminsky ticked off the skills Nakamoto would need to pull it off. “He’s a world-class programmer, with a deep understanding of the C++ programming language,” he said. “He understands economics, cryptography, and peer-to-peer networking.”
“Either there’s a team of people who worked on this,” Kaminsky said, “or this guy is a genius.”
Kaminsky wasn’t alone in this assessment. Soon after creating the currency, Nakamoto posted a nine-page technical paper describing how bitcoin would function. That document included three references to the work of Stuart Haber, a researcher at H.P. Labs in Princeton. Haber is a director of the International Association for Cryptologic Research and knew all about bitcoin. “Whoever did this had a deep understanding of cryptography,” Haber said when I called. “They’ve read the academic papers, they have a keen intelligence, and they’re combining the concepts in a genuinely new way.”
Haber noted that the community of cryptographers is very small: about three hundred people a year attend the most important conference, an annual gathering in Santa Barbara. In all likelihood, Nakamoto belonged to this insular world. If I wanted to find him, the Crypto 2011 conference would be the place to start.
“Here we go, team!” a cheerleader shouted before two burly guys heaved her into the air.
It was a foggy Monday morning in mid-August, and dozens of college cheerleaders had gathered on the athletic fields of the University of California at Santa Barbara for a three-day training camp. Their hollering could be heard on the steps of a nearby lecture hall, where a group of bleary-eyed cryptographers, dressed in shorts and rumpled T-shirts, muttered about symmetric-key ciphers over steaming cups of coffee.