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Teleportation breakthrough made
2004 06 20

Scientists have performed successful teleportation on atoms for the first time, the journal Nature reports.

The feat was achieved by two teams of researchers working independently on the problem in the US and Austria.

The ability to transfer key properties of one particle to another without using any physical link has until now only been achieved with laser light.

Experts say being able to do the same with massive particles like atoms could lead to new superfast computers.

This development is a long way from the transporters used by Jean-Luc Picard and Captain Kirk in the famous Star Trek TV series.

When physicists talk about "teleportation", they are describing the transfer of "quantum states" between separate atoms.

These would be such things as an atom's energy, motion, magnetic field and other physical properties.

And in the computers of tomorrow, this information would form the qubits (the quantum form of the digital bits 1 and 0) of data processing through the machines.

Atomic dance
What the teams at the University of Innsbruck and the US National Institute of Standards and Technology (Nist) did was teleport qubits from one atom to another with the help of a third auxiliary atom.

It relies on a strange behaviour that exists at the atomic scale known as "entanglement", whereby two particles can have related properties even when they are far apart. Einstein called it a "spooky action".

The two groups used different techniques for achieving teleportation, but both followed the same basic protocol.

Step 1: A pair of entangled ions are created: B and C
Step 2: The state to be teleported is created in ion A
Step 3: One ion from the pair - in this case B - is entangled with A and both are measured
Step 4: The quantum state of A is sent to ion C
Step 5: The state created for A is teleported to C

First, a pair of highly entangled, charged atoms (or ions) are created: B and C. Next, the state to be teleported is created in a third ion, A.

Then, one ion from the pair - let's say B - is entangled with A, and the internal state of both is measured.

Finally, the quantum state of ion A is sent to ion C, transforming it. This destroys the original quantum state of A.

The teleportation took place in milliseconds and at the push of a button, the first time such a deterministic mechanism has been developed for the process.

'Great potential'

The landmark experiments are being viewed as a major advance in the quest to achieve ultra-fast computers, inside which teleportation could provide a form of invisible "quantum wiring".

These machines would be able to handle far bigger and more complex loads than today's super-computers, and at many times their speed.

"In a quantum computer it's straightforward enough to move quantum information around by simply moving the qubits, but you might want to do things very quickly, so you could use teleportation instead," said Nist's Dr David Wineland.

Professor Rainer Blatt, of the University of Innsbruck, told BBC News Online: "This is a milestone.

"We are able to teleport in a deliberate way - that is, at the push of a button. This has been done before, but not in such a way that you can keep the information there at the end."

Professor Blatt's team, an Austrian-US group, performed the teleportation on calcium ions. The Nist team in Boulder, Colorado, used ions of the element beryllium.

Despite this and some differences in the experimental methods used by the two groups, both teams reached similar values of fidelity - around 0.75.

Fidelity is a measure of how well the quantum state of the second ion after teleportation resembles the original quantum state.

Commenting in an article published in Nature, physicists H Jeff Kimble and Steven Van Enk said: "These two experiments represent a magnificent confluence of experimental advances, ranging from precision spectroscopy and laser cooling.

"The fact that such diverse procedures performed so superbly in two separate laboratories attests to the flexibility and great potential of ion trapping for processing quantum information."

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