Teleportation Milestone Achieved

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Scientists have come a bit closer to achieving the "Star Trek" feat of teleportation. No one is galaxy-hopping, or even beaming people around, but for the first time, information has been teleported between two separate atoms across a distance of a meter — about a yard.

This is a significant milestone in a field known as quantum information processing, said Christopher Monroe of the Joint Quantum Institute at the University of Maryland, who led the effort.

Teleportation is one of nature's most mysterious forms of transport: Quantum information, such as the spin of a particle or the polarization of a photon, is transferred from one place to another, without traveling through any physical medium. It has previously been achieved between photons (a unit, or quantum, of electromagnetic radiation, such as light) over very large distances, between photons and ensembles of atoms, and between two nearby atoms through the intermediary action of a third.

None of those, however, provides a feasible means of holding and managing quantum information over long distances.

Now the JQI team, along with colleagues at the University of Michigan, has succeeded in teleporting a quantum state directly from one atom to another over a meter. That capability is necessary for workable quantum information systems because they will require memory storage at both the sending and receiving ends of the transmission.

In the Jan. 23 issue of the journal Science, the scientists report that, by using their protocol, atom-to-atom teleported information can be recovered with perfect accuracy about 90 percent of the time — and that figure can be improved.

"Our system has the potential to form the basis for a large-scale 'quantum repeater' that can network quantum memories over vast distances," Monroe said. "Moreover, our methods can be used in conjunction with quantum bit operations to create a key component needed for quantum computation."

A quantum computer could perform certain tasks, such as encryption-related calculations and searches of giant databases, considerably faster than conventional machines. The effort to devise a working model is a matter of intense interest worldwide.

Teleportation and entanglement

Physicist Richard Feynman is quoted as having said that "if you think you understand quantum mechanics, you don't understands quantum mechanics." Or sometimes he is cited thusly: "I think I can safely say that nobody understand quantum mechanics."

Nonetheless, here is how the University of Maryland describes Monroe's work.

Teleportation works because of a remarkable quantum phenomenon called entanglement which only occurs on the atomic and subatomic scale. Once two objects are put in an entangled state, their properties are inextricably entwined. Although those properties are inherently unknowable until a measurement is made, measuring either one of the objects instantly determines the characteristics of the other, no matter how far apart they are.

The JQI team set out to entangle the quantum states of two individual ytterbium ions so that information embodied in the condition of one could be teleported to the other. Each ion was isolated in a separate high-vacuum trap, suspended in an invisible cage of electromagnetic fields and surrounded by metal electrodes.

The researchers identified two readily discernible ground (lowest energy) states of the ions that would serve as the alternative "bit" values of an atomic quantum bit, or qubit.

Conventional electronic bits (short for binary digits), such as those in a personal computer, are always in one of two states: off or on, 0 or 1, high or low voltage, etc. Quantum bits, however, can be in some combination, called a "superposition," of both states at the same time, like a coin that is simultaneously heads and tails — until a measurement is made. It is this phenomenon that gives quantum computation its extraordinary power.