1 × N DWDM channel selective quantum frequency conversion

Dense wavelength division multiplexing (DWDM) is a key technology for realizing high-capacity and flexible quantum communication networks. To enable the emerging quantum internet, quantum frequency conversion is also essential for bridging different quantum systems over optical fiber networks. In this work, aiming at a frequency-multiplexed quantum internet, we present a channel-selective quantum frequency conversion (CS-QFC) based on difference frequency generation in a PPLN waveguide, which has been widely used in conventional QFC experiments. The CS-QFC converts a frequency of a photon at a single frequency to any frequency in the DWDM channels by dynamically selecting one of the pump lights. In the experiment, we demonstrated the CS-QFC from 780 nm to around 1540 nm employing one of the pump lights around 1580 nm detuned with a spacing of 25 GHz. From the experiment using the laser light, we showed that the output-frequency tunability of our CS-QFC reaches 2.5 THz, which corresponds to the ability to establish a 100-ch DWDM dynamic link from a single quantum system. Using photon pairs, we performed an experiment in which photons were routed into seven of the DWDM channels. As a result, photons were converted to the channels corresponding to the pump frequencies, while keeping the nonclassical cross-correlation functions, and no crosstalk to the other channels was observed.