Downconversion quantum interface for a single quantum dot spin and 1550-nm single-photon channel

摘要

Long-distance quantum communication networks require appropriate interfacesbetween matter qubit-based nodes and low-loss photonic quantum channels. Weimplement a downconversion quantum interface, where the single photons emittedfrom a semiconductor quantum dot at 910 nm are downconverted to 1560 nm using afiber-coupled periodically poled lithium niobate waveguide and a 2.2-$\mu$mpulsed pump laser. The single-photon character of the quantum dot emission ispreserved during the downconversion process: we measure a cross-correlation$g^{(2)}(\tau = 0) = 0.17$ using resonant excitation of the quantum dot. Weshow that the downconversion interface is fully compatible with coherentoptical control of the quantum dot electron spin through the observation ofRabi oscillations in the downconverted photon counts. These results represent acritical step towards a long-distance hybrid quantum network in whichsubsystems operating at different wavelengths are connected through quantumfrequency conversion devices and 1.5-$\mu$m quantum channels.