Light step toward quantum networks

Peter Weiss

Researchers are striving to use quantum physics to store, manipulate, and transmit data to someday create extraordinarily powerful and secure computer networks. Now, physicists in Atlanta have demonstrated the quantum version of one of the most basic network functions: reading a bit from a computer's memory so that it can be sent through a communications channel.

Dzmitry N. Matsukevich and Alex Kuzmich of the Georgia Institute of Technology describe the feat in the Oct. 22 Science.

Unlike conventional bit reading, the procedure manipulates quantum data bits, or qubits, which can each simultaneously represent a 0 and a 1. In a likely architecture for quantum networks, individual or small aggregates of atoms or ions will act as qubits for storage and calculations, whereas photons will serve as communications qubits between the atoms or ions.

In the new experiment, the researchers forced a cloud of ultracold rubidium-85 atoms into a specific quantum state. Then, they triggered those atoms to collectively emit one photon endowed with its own version of the cloud's quantum state.

"For the first time … we've transferred a matter qubit to a photon qubit," Kuzmich says. Next to come, he adds, is the converse operation.

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References:

Matsukevich, D.N., and A. Kuzmich. 2004. Quantum state transfer between matter and light. Science 306(Oct. 22):663–666. Abstract available at http://dx.doi.org/10.1126/science.1103346.

Further Readings:

Weiss, P. 2004. Quantum snare entraps key fifth photon. Science News 166(July 17):46. Available to subscribers at http://www.sciencenews.org/articles/20040717/note15.asp.

______. 2004. Teleporting matter's traits: Beaming information quantum-style. Science News 165(June 19):387. Available at http://www.sciencenews.org/articles/20040619/fob1.asp.

______. 2004. Quantum link connects light, ions. Science News 165(March 27):206. Available to subscribers at http://www.sciencenews.org/articles/20040327/note16.asp.

______. 2001. Atomic crowds tied by quantum thread. Science News 160(Sept. 29):196. Available at http://www.sciencenews.org/articles/20010929/fob1.asp.

Sources:

Alex Kuzmich
School of Physics
Georgia Institute of Technology
Atlanta, GA 30332

From Science News, Volume 166, No. 20, November 13, 2004, p. 316.