Moving photons in single file

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30 April 2008 News

Frost & Sullivan Technical Insights

Quantum information processing has the potential to allow vastly more powerful computing systems, communications that cannot be overheard, and many other possibilities, all courtesy of the rules that govern physics in the quantum world. However, the basic tools and techniques that will allow various quantum information processing systems to move from theory to practical use are still being developed.

Writing in the journal Science (Volume 319: pages 1062-1065), an international team of researchers report on the development of one such part of the quantum toolkit, a 'photon turnstile' that can regulate the flow of photons through a cavity one-by-one. Frost & Sullivan has taken particular interest in this, as the work could greatly benefit quantum systems that depend on reliable sources of single photons.

"The results have applications in quantum information science, including for controlled interactions of single light quanta and for scalable quantum processing on atom chips," said Jeff Kimble, one of the authors of the report.

Kimble and colleagues use a microscopic optical resonator in the shape of a toroid. The device is lithographically fabricated, with input and output coupling via optical fibre. One atom placed within the cavity of the device is able to dynamically control which photons are transmitted and which are reflected within the system, essentially forcing each photon to march through the device in single file.

"This regulation is achieved by way of an interference effect involving the directly transmitted optical field, the intracavity field in the absence of the atom, and the polarisation field radiated by the atom," explained Kimble. The system operates robustly and efficiently, allowing only one photon at a time to exit from the resonator system to the output fibre.

The system is not the first photonic turnstile. Other teams have been working on such systems for almost a decade. However, the finding that the interaction of just one atom with a resonator is enough to create a reliable turnstile could make such systems simpler to fabricate and more easily accessible to developers.

For more information contact Patrick Cairns, Frost & Sullivan Technical Insights, +27 (0)21 680 3274, [email protected]

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Moving photons in single file

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