Quantum theory of non-Hermitian optical binding between nanoparticles

TL;DR

This paper develops a quantum theoretical framework for non-Hermitian, nonreciprocal optical interactions between nanoparticles, enabling exploration of quantum physics in nanoparticle arrays with tunable coupling.

Contribution

It introduces a Markovian quantum master equation for non-Hermitian nanoparticle interactions, including quantum noise, and demonstrates how to achieve nonreciprocal and unidirectional coupling.

Findings

Derived the quantum master equation for nanoparticle interactions

Showed how to realize nonreciprocal coupling quantum mechanically

Provided tools for studying quantum effects in nanoparticle arrays

Abstract

Recent experiments demonstrate highly tunable nonreciprocal coupling between levitated nanoparticles due to optical binding [Rieser et al., Science 377, 987 (2022)]. In view of recent experiments cooling nanoparticles to the quantum regime, we here develop the quantum theory of small dielectric objects interacting via the forces and torques induced by scattered tweezer photons. The interaction is fundamentally non-Hermitian and accompanied by correlated quantum noise. We present the corresponding Markovian quantum master equation and show how to reach nonreciprocal and unidirectional coupling. Our work provides the theoretical tools for exploring and exploiting the rich quantum physics of nonreciprocally coupled nanoparticle arrays.