Cascaded downconversion interface to convert single-photon-level signals at 650 nm to the telecom band.

We present a device designed for two-step downconversion of single-photon-level signals at 650 nm to the 1.5-μm band with low excess noise and low required pump power as a quantum interface between matter-qubit-based nodes and low-loss photonic channels for quantum communication networks. The required pump power for this interface is around 60% of that for a comparable conventional single-pass device, which reduces the demand on the pump laser and yields a corresponding reduction in dark counts due to inelastic pump scattering.

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

Long-distance quantum communication networks require appropriate interfaces between matter qubit-based nodes and low-loss photonic quantum channels. We implement a downconversion quantum interface, where the single photons emitted from a semiconductor quantum dot at 910 nm are downconverted to 1560 nm using a fiber-coupled periodically poled lithium niobate waveguide and a 2.2-μm pulsed pump laser.