Entanglement of Propagating Optical Modes via a Mechanical Interface

TL;DR

This paper demonstrates the generation of entanglement between two propagating optical modes via a cryogenic mechanical interface, maintaining entanglement at room temperature, which advances quantum networking capabilities.

Contribution

It introduces a method to entangle optical modes through a mechanical system, enabling room-temperature quantum communication over optical fibers.

Findings

Entanglement persists at room temperature.

Logarithmic negativity of 0.35 detected without corrections.

Mechanical interface effectively couples propagating optical modes.

Abstract

Many applications of quantum information processing (QIP) require distribution of quantum states in networks, both within and between distant nodes. Optical quantum states are uniquely suited for this purpose, as they propagate with ultralow attenuation and are resilient to ubiquitous thermal noise. Mechanical systems are then envisioned as versatile interfaces between photons and a variety of solid-state QIP platforms. Here, we demonstrate a key step towards this vision, and generate entanglement between two propagating optical modes, by coupling them to the same, cryogenic mechanical system. The entanglement persists at room temperature, where we verify the inseparability of the bipartite state and fully characterize its logarithmic negativity by homodyne tomography. We detect, without any corrections, correlations corresponding to a logarithmic negativity of $E_\mathrm{N}=0.35$. Combined with quantum interfaces between mechanical systems and solid-state qubit processors already available or under development, this paves the way for mechanical systems enabling long-distance quantum information networking over optical fiber networks.