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To catch a particle of light


Date: March 27, 2016
Weizmann Magazine Vol. 9

Dr. Barak Dayan has figured out how to pluck a single photon—a particle of light—out of a light pulse, a longtime goal of particle physicists who were galvanized by the mere challenge and also aware of its potential applications.

Already today, light pulses are the workhorses of communications systems. “But once we move over to quantum computation and communications systems, which will harness the ‘weird’ rules of quantum physics, information will have to be encoded in single photons,” says Dr. Dayan, a member of the Department of Chemical Physics.

“Each photon will then represent a single ‘qubit’—a quantum bit that can exist in more than one state at the same time (for example, an equal combination of both 1 and 0),” he explains, enabling new types of computing that are nearly inconceivable today.

To build a trap for a single photon, the researchers began with a single atom—guided and cooled to near-zero temperatures with lasers. In previous work, Dr. Dayan and his group had used the single-atom system as a “photonic router” that switched a single photon to different directions, depending on the command given by the single photon before it.

In the new study, they managed to divert just one photon out of a pulse that contained numerous photons, demonstrating the ability of their system to turn itself off quickly enough to let all the rest of the photons continue undisturbed through the optical fiber.

The applications of this scheme for quantum communications range from eavesdropping for security and other purposes to photonic quantum communication systems, to the purification of quantum cryptography systems. Dr. Dayan says he is particularly excited by the new avenues of scientific research that will be opened by the ability to control individual particles of light.


Dr. Barak Dayan is funded by The Benoziyo Endowment Fund for the Advancement of Science, Crown Photonics Center, Deloro Institute for Advanced Research in Space and Optics, Rothschild Caesarea Foundation. Dr. Dayan is the incumbent of the Joseph and Celia Reskin Career Development Chair.


Dr. Barak Dayan

Dr. Barak Dayan