Wide-band quantum interface for visible-to-telecommunication wavelength conversion

We perform the first demonstration of a quantum interface for frequency down-conversion from visible to telecommunication bands by using a nonlinear crystal. This interface has a potential to work over wide bandwidths, leading to a high-speed interface of frequency conversion. We achieve the conversion of a pico-second visible photon at 780 nm to a 1522-nm photon, and observe that the conversion process retain entanglement between the down-converted photon and another photon.