In a recent article in Applied Physics Letters,* CNST researchers demonstrated how commercially available electro-optic modulators can be used to tailor the single photon output of quantum dots (QDs) for use in broadband quantum memories and other systems. Nanoscale light-emitters such as semiconductor QDs are leading candidates for the stable generation of single photons "on demand" for use in communications, information processing, and metrology. To create such photons, a train of laser pulses can be used to optically excite a single, epitaxially-grown semiconductor QD, which then emits a train of single photon pulses. However, the temporal profile of these single photon pulses, described as a photon wave packet, is typically not ideal for use in quantum information processing. Using commercial, high-performance telecommunications electro-optic modulators, the researchers were able to temporally manipulate these wave packets to produce a variety of shapes, including optimally-shaped Gaussian pulses. Compared to previous work, this approach reduced the modulation timescale more than two orders of magnitude, reaching the sub-nanosecond regime needed for semiconductor QDs. Finally, the researchers proposed that such electro-optic modulation may be a method for improving the quality of single photons from existing QD sources. Because of decoherence, single photons generated by a QD are not identical, and instead have different wave packets. Electro-optic modulation could be a flexible and spectrally broadband way to select for the decoherence-free portion of the QD emission, and thereby improve the photon indistinguishability needed for quantum information processing applications.
*Subnanosecond electro-optic modulation of triggered single photons from a quantum dot, M. T. Rakher and K. Srinivasan, Applied Physics Letters 98, 211103 (2011).
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