Researchers at NTT demonstrated the wavelength conversion of a single-photon wave packet required for quantum information-communication technologies. The company said the technique enables it deterministically change the color and shape of a single-photon wave packet in a lossless manner.
NTT lossless scheme utilized an all-optical effect called cross-phase modulation (XPM) to control the phase of light (signal pulses) via a change in the refractive index of a medium induced by another light (control pulses).
"When the refractive index varies dynamically, frequency modulation is induced to the signal field as a result of a signal’s non-uniform phase shift. By using single photons as the signal field, we can modulate the wavelength of the photons (Fig. 1). Since XPM always occurs regardless of the intensity of the control field, the wavelength conversion occurs without a photon loss. This is in contrast to the conventional all-optical wavelength conversion scheme for photons, namely nonlinear frequency mixings, where an intense control field is required for high conversion efficiency."
Researchers at Nippon Telegraph and Telephone Corporation (NTT) and the University of Toronto are proposing all-photonic quantum repeaters for long-distance quantum communication. If achieved, such devices would disprove the necessity of matter quantum memories in long distance quantum communications, which is seen by many as the ultimate future of optical communications.
In a paper published this week by the journal Nature Communications, the researchers said their all-photonic scheme paves a completely new route towards long-distance quantum communication based only on optical devices. Compared to matter quantum memories, this approach eliminates the quantum interface between matter and photons. The design is based on existing optical technology, such as linear optical elements, single-photon sources, photon detectors and an active feed-forward technique.
http://www.ntt.co.jp/news2015/1504e/150415a.html
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