Non-classical correlations between single photons and phonons from a mechanical oscillator

TL;DR

This paper demonstrates non-classical correlations between single photons and phonons in a nanomechanical resonator, showing potential for quantum communication and transducer applications.

Contribution

It presents the first full quantum protocol linking single photons and phonons in a mechanical resonator, including ground state initialization and correlation measurement.

Findings

Violation of Cauchy-Schwarz inequality confirms non-classical correlations.

Successful generation and read-out of photon-phonon pairs.

On-chip solid-state mechanical resonators can serve as quantum interfaces.

Abstract

Interfacing a single photon with another quantum system is a key capability in modern quantum information science. It allows quantum states of matter, such as spin states of atoms, atomic ensembles or solids, to be prepared and manipulated by photon counting and, in particular, to be distributed over long distances. Such light-matter interfaces have become crucial to fundamental tests of quantum physics and realizations of quantum networks. Here we report non-classical correlations between single photons and phonons -- the quanta of mechanical motion -- from a nanomechanical resonator. We implement a full quantum protocol involving initialization of the resonator in its quantum ground state of motion and subsequent generation and read-out of correlated photonphonon pairs. The observed violation of a Cauchy-Schwarz inequality is clear evidence for the non-classical nature of the mechanical state generated. Our results demonstrate the availability of on-chip solid-state mechanical resonators as light-matter quantum interfaces. The performance we achieved will enable studies of macroscopic quantum phenomena as well as applications in quantum communication, as quantum memories and as quantum transducers.