Efficient Interface between Ultrafast and Nanosecond Optical Quantum Systems

A promising approach to realize a quantum internet [1] is to use a hybrid quantum network - a network composed of many different quantum devices, such as quantum emitters, quantum repeaters, or quantum gates, interconnected via photonic links. However, such a wide variety of quantum devices tends to be spectrally incompatible. Especially, the challenge arises to interface different single-photon spectral bandwidths with high efficiency. In particular, an important link is bridging the ultrafast optics with hundreds of GHz spectral bandwidths with nanosecond timescales of single-photon pulses, hence MHz-wide spectra. Such an interface corresponds, e.g., to coupling a single photon produced in a commonly used bulk spontaneous parametric down-conversion (SPDC) photon sources to atomic-based quantum memories. The already demonstrated spectral compression techniques, based mostly on optical nonlinearities, operate only in the above GHz regime and are not suitable for this task [2].