A Big Jump For Quantum Teleportation

By Roland Piquepaille

Many interesting new developments occurred recently in the quantum computing field. While IEEE Spectrum asked if quantum dots could compute, the Fraunhofer Institute offered Internet access to the world's most powerful (31 qubit) Quantum Computing Simulator. In "Spooky Spaceflight," Astrobiology Magazine suggests that "quantum entanglement could hold out the promise of a novel means of space propulsion, perhaps even making interstellar travel feasible." And EE Times is reviewing how quantum encryption is poised to tighten data security. Elsewhere, in Austria, BBC News reports that teleportation is going long distance with an experiment in which photons have crossed 600 meters over the Danube River, the first time outside laboratories. Please read all the above articles if you're interested in quantum computing. For my part, I'm focusing on the quantum teleportation across the Danube River.

Before going further, here is how quantum teleportation works.

First, an entangled state of ions A and B is generated, then the state to be teleported -- a coherent superposition of internal states -- is created in a third ion, P. The third step is a joint measurement of P and A, with the result sent to the location of ion B, where it is used to transform the state of ion B (step 4). The state created for P has then been teleported to B. (Credit for image and legend: H. J. Kimble and S. J. van Enk, Nature)

Now, let's look at the BBC News article.

Long distance teleportation is crucial if dreams of superfast quantum computing are to be realised. When physicists say "teleportation", they are describing the transfer of key properties from one particle to another without a physical link.

Researchers from the University of Vienna and the Austrian Academy of Science used an 800m-long optical fibre fed through a public sewer system tunnel to connect labs on opposite sides of the River Danube.

The link establishes a channel between the labs, dubbed Alice and Bob. This enables the properties, or "quantum states", of light particles to be transferred between the sender (Alice) and the receiver (Bob).

This illustration shows how the experiment was conducted. (Credit: University of Vienna)

In "Teleportation Takes Quantum Leap," National Geographic explains why this experiment is a world's premiere.

"We were able to perform a quantum teleportation experiment for the first time ever outside a university laboratory," said Rupert Ursin, a researcher at the Institute for Experimental Physics at the University of Vienna in Austria.

The science is not new, said Mark Kuzyk, a physics professor at Washington State University in Pullman. But this is the first time "researchers have demonstrated that teleportation works in the kinds of real-life conditions that are found in telecom applications."

The research work has been published by Nature. Here is a link to the abstract of the paper called "Quantum teleportation across the Danube," which, surprisingly, is written in plain English.

Efficient long-distance quantum teleportation is crucial for quantum communication and quantum networking schemes. Here we describe the high-fidelity teleportation of photons over a distance of 600 metres across the River Danube in Vienna, with the optimal efficiency that can be achieved using linear optics. Our result is a step towards the implementation of a quantum repeater, which will enable pure entanglement to be shared between distant parties in a public environment and eventually on a worldwide scale.

Finally, here is the usual reference to Star Trek.

"Nothing we do will help us build Scotty's apparatus," Ursin said. "The reason is very simple: A human body contains too much information to scan and build all replicas."

For a human to be teleported, a machine would have to pinpoint and analyze the trillions and trillions of atoms that make up the human body. Only recently have scientists taken preliminary steps toward teleporting even a single, whole atom.

Sources: Erico Guizzo, IEEE Spectrum Online, August 4, 2004; Fraunhofer Institute for Computer Architecture and Software Technology (FIRST); Mark Waldron, Astrobiology Magazine, August 6, 2004; Chappell Brown, CommsDesign, an EE Times Community, August 23, 2004; Paul Rincon, BBC News Online, August 18, 2004; Stefan Lovgren, for National Geographic News, April 18, 2004; Nature, August 19, 2004