Quantum link connects light, ions

Peter Weiss

Instantly teleporting people and objects from one planet to another is a staple of science fiction. Now, physicists at the University of Michigan in Ann Arbor have taken a promising step toward teleporting at least some traits from atom to atom.

The new technique relies on a well-known but still mysterious phenomenon called entanglement, in which specific quantum traits of elementary particles become correlated, even at vast distances (SN: 12/8/01, p. 364: http://www.sciencenews.org/articles/20011208/bob16.asp). In this experiment, the researchers used a laser pulse to induce a cadmium ion to emit a photon whose polarization was entangled with the ion's spin, a magnetic quantum property. Polarization is the orientation of a photon's electromagnetic field, and an ion's spin is akin to a top's motion.

Entangling the photon and ion is a step toward entangling two widely separated ions, say Boris B. Blinov and his colleagues. To do that, the team would need to entangle each ion with its own photon and then entangle the photons. That last step would destroy the photons and entangle the two ions, Blinov says. Such ion-to-ion links could serve as portals for teleportation and for data exchanges between future quantum computers. The scientists detail their advance in the March 11 Nature.

The Michigan team is the first to prove the entanglement of a photon and an ion. However, scientists suspect that such quantum links have formed in previous experiments, Blinov notes.

The researchers are now devising a new setup that can simultaneously stimulate each of two ions, located meters apart, to emit an entangled photon to be entangled with its counterpart.

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References:

Blinov, B.B., D.L. Moehring, L.-M. Duan, and C. Monroe. 2004. Observation of entanglement between a single trapped atom and a single photon. Nature 428(March 11):153–157. Abstract available at http://dx.doi.org/10.1038/nature02377.

Polzik, E. 2004. Flight of the qubit. Nature 428(March 11):129–130.

Further Readings:

Peterson, I. 1998. Instant transport. Science News 153(Jan. 17):41.

Weiss, P. Gadgets from the quantum spookhouse. Science News 160(Dec. 8):364–366. Available at http://www.sciencenews.org/articles/20011208/bob16.asp.

______. 1999. Quantum Internet. Science News 155(April 3):220–221. References and sources available at http://www.sciencenews.org/pages/sn_arc99/4_3_99/bob2ref.htm.

Sources:

Boris B. Blinov
FOCUS Center
University of Michigan, Ann Arbor
Department of Physics
Ann Arbor, MI 48109-1120

David L. Moehring
FOCUS Center
University of Michigan, Ann Arbor
Department of Physics
Ann Arbor, MI 48109-1120

Christopher Monroe
FOCUS Center
University of Michigan, Ann Arbor
Department of Physics
Ann Arbor, MI 48109-1120

Eugene Polzik
Niels Bohr Institute
Danish National Research Foundation Center for Quantum Optics (QUANTOP)
Blegdamsvej 17
Copenhagen 2100
Denmark

From Science News, Volume 165, No. 13, March 27, 2004, p. 206.