It was generally believed that the role of linear optics in quantum information processing was rather limited, due to the difficulty in implementing conditional quantum dynamics using single photons. However, recent work of Knill, Laflamme, and Milburn demonstrated that efficient quantum computation is possible using linear optics (LOQC), provided that triggered light sources that provide single-photons on demand are available.
In this talk, I will discuss the prospects for using single-photons generated by a quantum dot in LOQC. It has been demonstrated experimentally that a quantum dot is an ideal source of triggered single photon pulses. Since the requirements on source efficiency and single-photon linewidth imposed by LOQC proposal are extremely stringent, it is essential to use the cavity-QED techniques to enhance the collection efficiency and to ensure that the exciton line broadening is solely due to (Purcell-effect-enhanced) radiative recombination.
The elementary process in LOQC scheme is the interference of two photons impinging on a beam-splitter. The observability of this interference requires that the two photons be indistinguishable. From an experimental perspective, this implies that the single photon pulses generated by the QD should be Fourier-transform limited and have identical spatio-temporal profiles, which can only be the case if the exciton line is radiatively broadened and there is no jitter in emission time. Equally important for LOQC applications is the near unity efficiency of the single-photon source: fortunately, the Purcell effect that ensures the generation of transform-limited single-photon pulses, can also guarantee that a large fraction of the generated photons are captured.
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