Generation of identical photons using an electrically driven single-photon source

A single-photon source capable of emitting indistinguishable photons is a key element in schemes for scalable quantum information processing with linear optics. Whilst several groups have reported such sources, up until now an electrically driven source capable of making these protocols technologically viable has yet to be reported. We present the first demonstration of an electrically driven single-photon source emitting indistinguishable photons. Our sample consists of a layer of InAs/GaAs quantum dots embedded in the intrinsic region of a p-i-n microcavity diode. We test the indistinguishability of consecutive photons by carrying out a Hong-Ou- Mandel-type two-photon interference experiment whereby two identical photons arriving simultaneously at two input ports of a 50:50 beamsplitter exit together. The device was operated under two modes, continuous and pulsed current injection. In the former case, we measured a coherence time of up to 400 ps at low pump current - the longest reported under these excitation conditions. A two-photon interference visibility was measured, limited only by the timing resolution of our detection system and further suggesting a 100% overlap of photon wavepackets at the output beamsplitter. In the case of pulsed injection, we employed a two-pulse voltage sequence which allowed us to carry out temporal filtering of photons which had undergone dephasing. The characteristic Hong-Ou-Mandel "dip" was measured resulting in a visibility of 64 ± 4%.