Temporal stretching of single-photon pulses by intra-cavity frequency conversion

Abstract

Spectral bandwidth and frequency mismatch between quantum light emitters and quantum components is a common problem in the realization of hybrid quantum information networks. Here we propose a simultaneous solution to both of these problems by using a free-space cavity with an embedded nonlinear crystal that, through frequency conversion, facilitates perfect coupling into a cavity mode. The slow leakage of the cavity effectively stretches the photon pulse, resulting in a much longer photon pulse at a different wavelength. We show that the amount of stretching is strictly limited by the finesse and length of the cavity. Including realistic internal losses in the cavity, we show that it is possible to stretch a photon by at least two orders of magnitude with high efficiency. The proposed setup can thus constitute a valuable addition to the toolbox of quantum information technologies.