Nonlinear stochastic and quantum motion from Coulomb forces

TL;DR

This paper demonstrates that Coulomb interactions inherently contain nonlinear effects that can be observed as non-reciprocal nonlinearities, enhancing quantum measurement sensitivity across various scales.

Contribution

It reveals that after removing harmonic components, Coulomb forces exhibit observable nonlinear and non-reciprocal effects in quantum and stochastic regimes.

Findings

Nonlinear effects are present in Coulomb interactions across different scales.

Elimination of harmonic parts reveals non-reciprocal nonlinearities.

Signal-to-noise ratio can be increased via Coulomb-induced nonlinearities.

Abstract

Controllable nonlinear quantum interactions are a much sought after target for modern quantum technologies. They are typically difficult and costly to engineer for bespoke purposes. However controllable nonlinearities may have always been in reach via the natural and fundamental forces between quantum particles. The Coulomb interaction between charged particles is the simplest example. We show that after eliminating the harmonic part of the Coulomb force by an auxiliary linear force, the remaining reciprocal nonlinear part results in a directly observable non-reciprocal nonlinear effect: increase of the signal-to-noise ratio (SNR) of the coherent displacement of one particle, driven by the position noise, or uncertainty in quantum regime, in another particle. This essential evidence of nonlinear forces is present across large ranges of trap frequency and mass scales, as well as visible in both stochastic and quantum regimes.