Synopsis

All-Around Single-Photon Source

Physics 9, s6
A quantum dot embedded in a micropillar is an efficient source of pure and indistinguishable single photons.
(Left) Sven Höfling and Christian Schneider/Universitat Würzburg; (Right) Niels Gregersen/Technical University of Denmark

Photonic quantum technologies require light sources that emit single photons on demand. Three prerequisites are deemed essential for applications: purity (the sources must emit one and only one photon at a time); indistinguishability (all photons must be identical, for instance, in frequency and polarization); and efficiency. These three features have never been achieved simultaneously in a single device. But Chao-Yang Lu, of the University of Science and Technology of China in Shanghai, and colleagues have now demonstrated a single-photon source that combines them all.

Their scheme uses infrared laser pulses to excite an electronic resonance of a semiconducting quantum dot, triggering the emission of single photons at infrared frequencies. In a previous demonstration using a quantum-dot architecture, Lu and colleagues achieved an efficiency of only 6%. Now, they’ve ramped this value up to 66%. In the new scheme, the researchers exploit the so-called Purcell effect, which enhances the emission rate of the quantum dot by embedding it in a micropillar cavity whose resonant frequency matches that of the dot. The cavity also efficiently funnels the dot’s emission into a single-mode fiber. In experimental tests, the device emitted 3.7 million pure and indistinguishable photons per second.

The scheme could be the basis for a “boson-sampling” machine, a quantum device that can solve certain computational tasks faster than any classical computer. The authors suggest that with a few tens of these perfect single photons, a boson-sampling device could carry out such tasks more efficiently than the best desktop computers on the market.

This research is published in Physical Review Letters.

–Matteo Rini


Subject Areas

Quantum InformationOptics

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