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

TL;DR

This paper demonstrates a downconversion quantum interface that converts single photons from a quantum dot at 910 nm to 1560 nm, preserving quantum properties and enabling integration into long-distance quantum networks.

Contribution

The work introduces a fiber-coupled downconversion interface that maintains single-photon quantum characteristics and supports coherent control, advancing quantum network integration.

Findings

Preserves single-photon character during downconversion (g^{(2)}(0)=0.17)

Compatible with coherent control of quantum dot spins

Enables connection of quantum dots to 1550-nm channels

Abstract

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-$\mu$m pulsed pump laser. The single-photon character of the quantum dot emission is preserved during the downconversion process: we measure a cross-correlation $g^{(2)}(\tau = 0) = 0.17$ using resonant excitation of the quantum dot. We show that the downconversion interface is fully compatible with coherent optical control of the quantum dot electron spin through the observation of Rabi oscillations in the downconverted photon counts. These results represent a critical step towards a long-distance hybrid quantum network in which subsystems operating at different wavelengths are connected through quantum frequency conversion devices and 1.5-$\mu$m quantum channels.