Harnessing electro-optic correlations in an efficient mechanical converter

TL;DR

This paper demonstrates a mechanically-mediated microwave-optical converter operating at cryogenic temperatures with nearly 50% efficiency, utilizing noise correlations for improved quantum information transfer.

Contribution

It introduces a novel feedforward protocol that exploits correlated noise in the converter outputs to reduce added noise, advancing quantum communication technology.

Findings

Achieved 47% conversion efficiency at T < 100 mK.

Discovered strong noise correlations between output ports.

Proposed a quantum feedforward protocol for robust quantum info transfer.

Abstract

An optical network of superconducting quantum bits (qubits) is an appealing platform for quantum communication and distributed quantum computing, but developing a quantum-compatible link between the microwave and optical domains remains an outstanding challenge. Operating at $T < 100$ mK temperatures, as required for quantum electrical circuits, we demonstrate a mechanically-mediated microwave-optical converter with 47$\%$ conversion efficiency, and use a feedforward protocol to reduce added noise to 38 photons. The feedforward protocol harnesses our discovery that noise emitted from the two converter output ports is strongly correlated because both outputs record thermal motion of the same mechanical mode. We also discuss a quantum feedforward protocol that, given high system efficiencies, allows quantum information to be transferred even when thermal phonons enter the mechanical element faster than the electro-optic conversion rate.