The science of teleportation

by GILBERT WONG

It looks like a match flaring briefly on a pitch-dark night. The image repeats. As a major breakthrough in the weird, counter-intuitive world of quantum physics it is ... underwhelming.

That is until Scott Parkins, of the Auckland University physics department, explains what we're looking at.

The flicker is a single caesium atom captured for about 150 millionths of a second in an orbit of one-200th of a millimetre.

Last month Science magazine, the American journal of record for scientific invention, reported the successful demonstration of the atom-cavity microscope dreamed up by Parkins and colleague Andrew Doherty and built last year by scientists at Caltech, the California Institute of Technology's Pasadena campus.

The report said: "It succeeds in trapping individual caesium atoms in microscopic orbits inside a high quality optical resonator, while simultaneously monitoring their motion with high resolution in real time."

That's another way of saying that they have found a way to look directly at the atomic world in action. For the first time, scientists will be able to spy on chemical reactions as they happen. It's a real television real-time view of the basic stuff of reality.

There are two ways to explain how it's done. The short way is to say it's done with mirrors. These mirrors are close to the edge of reflective perfection and placed about one-hundredth of a millimetre apart.

A trickle of supercooled caesium atoms drop through about one at a time. Caesium, a gas, has a simple and stable molecular structure.

"The atom is trapped in orbit with forces exerted by a tiny amount of light bouncing backwards and forwards between the mirrors," Parkins says.

The light comes from a laser shot through the two planes formed by the mirrors. By examining what happens to the laser light once it has passed through the second mirror, scientists can describe the movement of the caesium atom.

Only certain colours or frequencies of light can pass through the cavity, but exactly which colours depend on where the atom is inside the cavity.

While this may at first seem an exercise akin to counting the numbers of angels that can dance on the head of a pin - an analogy Parkins can smile at - it is, he says, another step into the mental bog of quantum teleportation.

Teleportation, as seen on Star Trek, moves a person or object almost instantaneously to a distant spot.

We can assume, Parkins says, that the teleporter works like a three-dimensional fax machine. Captain Kirk is scanned to extract all the information his body contains and this is beamed to another place where Kirk is recreated using the information.

As a perfect copy of Kirk is created, we assume that the transporter destroys the original Kirk to prevent a philosophical paradox.

The Caltech scientists Parkins worked with on the atom-cavity microscope are Jeff Kimble's team, the scientists responsible for demonstrating actual teleportation.

This largely unheralded achievement in 1998 involved shifting a photon, a basic particle of light, one metre, which on the face of it is a long way from Kirk requesting Scotty to "Beam me up" from the surface of a planet to the good starship Enterprise.

But theoretically, teleportation is possible using a phenomenon predicted by Albert Einstein, even if he didn't like the implications. He called the phenomenon "spooky action at a distance."

At first it seemed that teleportation would be impossible. If we assume that teleportation is like sending a three-dimensional fax, another quantum quirk - the Heisenberg Uncertainty Principle - states that you can never precisely measure where something is and how fast it is moving because the very act of measurement alters what you are trying to measure.

Counter to common sense - which quantum physics manages to be most of the time - there was a solution, first thought up in 1993 by IBM scientist Charles Bennett and others. It exploits a quantum quirk predicted by Einstein, Boris Podolsky and Nathan Rosen.

The Einstein-Podolsky-Rosen effect says that at the most basic level, an atom could be described by a mathematical expression known as a wave function, and that atoms could be described by a joint wave function.

This would imply that if you separated the atoms they would still be described by the same wave function. In quantum jargon they would be called entangled. Do something to one of the pair and the other is affected instantaneously, even if they are widely separated - Einstein's so-called "spooky action."

Technically, this would work if the entangled pair were at opposite sides of the Milky Way galaxy, which would in turn imply that quantum entanglement enables "instantaneous action at a distance," which implies that it is faster than light which is impossible according to Einstein's own theory of relativity. But that caveat aside, quantum teleportation can be done using "entangled" particles.

"Entanglement means that if you tickle one the other one laughs, Kimble says.

So Kimble's team took the original item, in this case a photon. This was combined with an entangled particle to produce gibberish. Because there was no measurement this did not breach the Heisenberg Uncertainty Principle.

The gibberish was sent to a receiving station where it was applied to the other particle in the pair. This allowed the original to be recreated the same way spies would encode and then decode a message.

The atom-cavity microscope offers one way to "read" the information at the atomic level, a precursor for quantum teleportations.

That said, the leap from photon to a person is a harder problem than making it possible for Armstrong to walk on the moon.

It has been estimated that describing the three-dimensional details of a human to a resolution of 1mm would require 10 gigabytes of information, or about 10 to 15 CD-Roms.

Taking resolution down to the necessary atomic level would require 10 to the power of 32 bits of information (10 followed by 32 zeros.)

The sums are daunting, but it is New Zealanders Parkins and Doherty that the world may one day thank if we actually do ever get to say, "Beam me up."