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Single Photon Converter – A Key Component of Quantum Internet

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spinning coins

A single photon a carrier of quantum information travels like a spinning coin, in a superposition of states.


Physicists from the University of Warsaw in Poland and the University of Oxford in the U.K. have constructed an electro-optical device capable of modifying the quantum properties of individual photons. In recent years, physicists have developed ways to generate light pulses with a specific wavelength or polarization to control the quantum bits used in quantum computing. Existing methods of modifying the properties of individual photons utilize nonlinear optical techniques, exposing photons to a strong optical pump beam. Whether the individual photons were modified remained a matter of chance.

In constructing the new device, researchers used the electro-optic effect occurring in certain crystals, which alters the intensity of an external magnetic force. The researchers were able to achieve a six-fold lengthening of the duration of a single-photon pulse while preserving a high level of conversion efficiency. Previous converters were only able to modify one among tens of photons, whereas the new device has demonstrated efficiency up to 200 times better. "In essence we process every photon entering the crystal," says Michal Jachura, a Ph.D. student at the University of Warsaw. "The efficiency is less than 100% not because of the physics of the phenomenon, but on account of hard-to-avoid losses of a purely technical nature, appearing for instance when light enters or exits optical fibers."

In addition to being efficient, the device is also stable, compact, and easy to install in an optical fiber system. Scientists say the new converter should help facilitate the development of hybrid quantum computers.

From University of Warsaw
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