Beam Us Up, Sandu

Teleportation is no longer total fantasy. Andy Martin meets Sandu Popescu, one of a new breed of DIY quantum physicists who are searching for a trap door in nature

MY TWIN brother lives in Oxford. I live in Cam-bridge. When Steve drops a hammer on his toe, I, sitting unharmed at my desk 100 miles away, yell "Ouch!" When I have a bad day he gets depressed. When we meet up we find we are wearing exactly the same old jeans and Timberland boots. We both married women called Alice.

Or rather, it ought to be that way, but alas isn't. We are twin brothers, but antithetical twins, dizygotic, radically opposed on nearly everything, out of sync. He's a rocket scientist, I'm a surfer; and if he's been tackled from behind by Paul Ince, the first I know of it is when he rings me up from hospital. The tragic reality is that we're remote planets drifting through space-time.

But I suspect that it was his sense that there should be more harmony and synchronicity in the universe at large - that full-on twinship should be the rule - that led him to build his flying saucer telephone a few years ago. We called it (borrowing the name from an Iain M Banks space opera) a "Farcom". Relativity is a major drag where extremely long-distance communication is concerned. Nothing can go faster than the speed of light, so if I want, in the immortal words of ET, to "phone home", and home happens to be Planet X in a system some 10 light years away, then it is going to take an irreducible minimum of 10 years for my message to get through - and the same for the reply to come back. In other words, we are marooned.

Steve had the answer all figured out, though. "Correlated particles" offer a bridge across lonely infinite space. Unlike the two of us, correlated particles really do behave like telepathic identical twins. Or, according to the basic tenets of quantum mechanics, they should. Take two photons (particles of light) from the same source (a laser, say). If particle A down on earth is turning somersaults, then at the very same instant, even, in theory, if it's billions of miles away on Planet X, particle B will go through the same routine. The two particles are so irrevocably fraternal that they will blink on or off, flip up or down, simultaneously, wherever they may be. Thus quantum mechanics overrides relativity. The occupants of the universe are not, after all, doomed to be isolated monads. Correlated particles could do a Houdini on the straitjacketed frames of reference (with different clocks) that Einstein had strapped us into. Plugged into that snappy interstellar quantum network, the Farcom was guaranteed to put us in touch with Alpha Centauri or Betelgeux, or wherever, without delay.

Steve set up shop in his garage with a view to jemmying open "a trap door in nature." He knew no one in Oxford or at the Rutherford Laboratories, where he worked as a physicist, would take it seriously. In the early Nineties, the Farcom was too far-out. So all alone, without fanfare or government subsidy, he juxtaposed a laser, a couple of beam-splitters, and a complicated system of mirrors, the whole lot delicately poised on an old motor-scooter tyre, which was in turn balanced on four breeze blocks, to maintain maximum equilibrium. At the CERN labs in Geneva they spend billions on this kind of gear. Steve spent about pounds 100 all told, with some precision engineering thrown in by our father. It was a brilliant experiment which would certainly have earned him fame and fortune, and possibly a Nobel Prize, when he got through to some passing extraterrestrial vehicle. Except he didn't.

In truth, my brother thought the Farcom was still a fanciful extrapolation of the facts. What he wanted to do to start with was a lot more modest, although impossible. It was the optical equivalent of dropping a hammer on the toe of one particle and waiting for its brother to jump up and down. He took the left-hand photon - Spike - and half of the time he stuck a polarizer (like the lens from an extremely large pair of shades) in its path. The rest of the time he let it sail straight through unimpeded. Meanwhile the right-hand photon - Spike's twin, Jake - was filtered through an interferometer (a barometer of particle behaviour). If everything went according to plan, half the time Jake - reacting from afar to Spike's experiences - would make pattern P (polarized) and the other half pattern Q (unpolarized). In the event, Jake made pattern P and pattern Q all right - but simultaneously, not alternatively. Instead of being either/or, it was and/and. Jake hadn't minded its Ps and Qs. It was a classic quantum phenomenon. But if you want to let someone in the constellation of Orion know what the weather is like on Earth, there's no point in saying it's sunny and raining.

"Looks like there is no trap door in nature, after all," my brother soberly concluded. He went back to his lab and carried on cooking up new chips. The quest for the Farcom was over. End of story.

Or so I thought, until, of all the lectures in all the world, I had to walk into one given recently by Sandu Popescu at the Isaac Newton Institute in Cambridge, one of the most prestigious mathematical arenas in the world, where the solution to Fermat's Last Theorem was unveiled in 1993. Sandu Popescu, the Hewlett-Packard Reader in Quantum Physics, is a big, bright, breezy Romanian, some trillion times larger than the particles he is so enamoured of. He was mapping out the current state of the art in quantum mechanics, and had brought those correlated and entangled particles out of my brother's garage and into the mainstream. Steve had been way ahead of his time.

In terms of popular perception, it used to be the case that the theory of relativity was the tough nut to crack, well beyond your average punter. Now relativity has become a doddle, the stuff of barroom talk. Everyone knows that e=mc2, and that a spaceman returning to earth after a quick flip around the galaxy will find most of his contemporaries in the grave. But quantum physics remains intellectually scandalous: no one understands quantum physics, not even quantum physicists. How are you supposed to make sense of a cat (Schrodinger's) in a box, a cat that is neither alive nor dead until you open the box and take a look inside? Or a tree that doesn't make any noise when it falls down, unless there is someone in the forest to hear it? The bizarre laws of quantum physics, allowing micro-particles off the leash of macro-laws and inflating the role of the observer, pile up paradoxes. This was the sort of thing that aroused Einstein's wrath. "Do you really believe that the moon ceases to exist just because you are not observing it?" he fumed.

In classical science, repeated experiments must produce identical results; in the quantum lab, results vary. For Einstein, this was tantamount to blasphemy. "God does not play dice," he famously remarked. He believed the "spooky" phenomenon of correlated particles could be explained by "hidden variables". With the Einstein-Podolsky-Rosen Paradox of 1935, he tried to show that these telepathic twins weren't communicating with each other distantly, they were wired up in advance to be triggered by different interactions.

"FOR THE next 30 years physicists turned into philosophers," Sandu complained, as we made ourselves coffee in the Newton cafe. So they spent all their time arguing over how many particles you could fit on the head of a pin or whether the whole thing was not some monstrous illusion. Then in 1964 John Bell - one of my brother's precursors - came up with a new set of experiments that blew Einstein's hidden variables right out of the water. He devised a complicated series of hoops, with random permutations built in, for one photon (or rather a small family of photons) to jump through. And still the fraternal particle born of a single light source jumped through those same undecideable-in-advance hoops over at the other end of the laboratory. It was the equivalent of Jake guessing the cards Spike was turning over in another room, correct every time.

The conclusion was inevitable: that entities can interact at a distance as if space and time didn't exist. The phenomenon that came to be known as "non-locality" was real. Then physics got bogged down once more in agonising over what it all meant, the "What is reality?" question.

Sandu was derisive. "Don't worry about the cat!" he exclaimed, as we headed off to lunch at Browns. Sandu didn't care whether Schrodinger's cat was alive or dead anyway. Quantum physicists have tended to be mazey theoreticians, strong on ideas, weak on practicalities. Steve and Sandu were a new breed: DIY fanatics of physics; quantum mechanics who got their hands dirty. Sandu's favourite phrase is "As a matter of fact..." Alongside such people, someone like the cosmologist Stephen Hawking appears as a theologian, obsessing about the "mind of god"; or a poet of a strongly metaphysical disposition. Sandu was frankly unconcerned that the whole body of quantum theory was contradictory, inconsistent, bound to collapse. He liked it that way. Any grand unified theory of the universe is just a mirage. For Sandu, mere understanding, or the lack of it, is a small thing: why should we expect to understand the intricacies of nature anyway? The more fruitful question, turning Einstein around, is why does God play dice? For, as Sandu put it: "It is obvious that he does. The interesting question is, what can we get out of it?" And his answer is: non-locality. Non-locality is everywhere, not only in my brother's garage. The beauty of non-locality is that it is the paradox of paradoxes - if you can swallow this one, all other quantum oddities follow logically. And non-locality opens a whole bunch of trap doors in nature. Teleportation, for one.

Cycling across Cambridge at lunchtime can be as hair-raising as the Monaco Grand Prix: other bikes were flying about at high speeds, as unpredictable as particles in an accelerator. "Maybe we should have teleported over?" I suggested.

"Yes - but I wouldn't like to go first," Sandu said. He explained that the main problem with the teleporter, in its current form, is that "it destroys the original". I could see why he would be reluctant to volunteer. It was worse than David Cronenberg's film The Fly. At least there, part of you comes out at the other end, even if your head is attached to a fly's body and vice versa. "But the copy is exact," he reassured me. You have to think of a teleporter as a three-dimensional fax rather than as ordinary mail: you feed the object in at one end and a replica comes out at the other. So every time Jean-Luc Picard is beamed down to a new planet, he dies and a new (but identical to the old) Picard is reincarnated, and yet another beams up again to say, "Engage - warp 9!"

All these things are "at the limit of possibility", but Sandu and a team have actually carried out an early-days teleportation experiment in Rome. So far, they have teleported only one photon, using correlated particles as a channel. Or rather, only the "soul" of a photon, to be re-embodied at the other end. But a principle has been established. And Sandu wouldn't be sponsored by Hewlett-Packard unless they expected to get a return on their investment.

Paradigm-shifts in science occur when previously unrelated fields are hooked up together. The 19th century fused electricity and light (Maxwell). The 20th century married gravity and space-time (Einstein). The big physics of the 21st century could see the grand synthesis of quantum physics and computer science. The quantum computer would do a completely different kind of maths, not subject to the old binary rules (instead of 1 or 0 you would have 1 and 0), which could find shortcuts and trap doors through all the old electronic labyrinths and speed up calculations a thousand- fold. Meanwhile, the most practical short-term pay-off is in cryptography. Sandu had just got back from Geneva, where a Swiss team had been shooting messages 23km to and from Lake Geneva, down a conventional fibre-optic cable, but with a particle attached. The photon was like the secret agent's hair-on-the-door trick: if anyone had tried to intercept the message, the photon would show evidence of interference. No one could get away with those code-breaking Enigma tricks ever again without being caught red-handed.

But these were conventional messages, sent at slower-than-light speeds. What I really desperately wanted to know about was the Farcom. "But can you send messages using the correlated particles?" I said. "Can you have non-local messages?"

"No," said Sandu, dashing my hopes. Then, in true quantum style, he resurrected them once more: "Or rather, yes and no." The crux is that the particles can send messages to one another all day long, from here to the next galaxy and back, with perfect mutual understanding. But we can't harness them. All we would need to send a "yes" or "no" message, or indeed the entire works of Shakespeare (since that is made up of an extremely large number of yes/no -type messages) is to impart an up or down orientation to one of those particles. But, as my brother discovered, it turns out that you can't do any such thing. These are rogue twins, who do what they please. "Non- locality without signalling," Sandu said, to my immense frustration. God played dice, but not in order to enable lost aliens to phone home. And teleportation, similarly, although operating with quantum simultaneity, nevertheless relied on back-up classical messages to disentangle the teleported state. Thus, quantum physics and relativity co-exist peacefully, not agreeing with one another, but not trying to overthrow one another either.

Sandu and I ended up at a dinner party where a no-nonsense Portuguese au pair bluntly put to him the embarrassing "How" question: "How is it possible for particles to communicate with one another simultaneously across space?" Sandu's answer to the problem is that for every two correlated particles there are another couple of invisible particles buzzing about back in time to pass on the news. But this is solving one mystery with another.

Steve had a different idea altogether. Instead of multiplying the two particles to make four , he rolled them up into one immense electro- magnetic field: the universe itself. "What you have is not two particles, but only one field. The two particles are nothing but quanta - points at which the field is interacting with matter. They don't have to communicate with one another because the field is a totality, always everywhere in touch with itself."

Steve and Sandu are both mad. But in a realm in which madness is everywhere you'd have to be crazy not to be. And, inside the padded cell of non-locality, there is a hope of answering one final absurd question; in fact the ultimate question of existence (in Heidegger's resonant formulation). Why is there something rather than nothing? In the wonderful world of quantum logic, as soon as you have zero, you automatically have the possibility of zero and one. Or, as Steve neatly put it, "If there really is nothing, then there is nothing to prevent there being something." The universe has to be seen as an enormously large ex nihilo particle which has briefly flickered into existence, and is doomed to blink off again. It fell out of a trap door. Non-locality, in other words, is the reason why God has any dice to play with in the first place.

And, by the same token, perhaps there is a twin universe elsewhere, leading a parallel life, in some correlated continuum that mirrors our own. We are not alone. In space, somebody can hear you scream. Or they could, if only you had a Farcom to yell down."

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