Achievability of Quantum Regime in Optomechanics of Electromagnetically Levitated Nanoparticles: Inclusion of Gradient Force Fluctuations

TL;DR

This paper investigates the limits of achieving quantum ground state in optomechanical levitated nanoparticles, highlighting the critical role of gradient force fluctuations and feedback mechanisms in experimental realizability.

Contribution

It provides a theoretical analysis of how gradient force fluctuations and feedback cooling influence the possibility of reaching the quantum regime in levitated nanoparticles.

Findings

Gradient force fluctuations set a lower pressure limit for quantum regime achievement.

Certain feedback cooling methods can be hindered by feedback-induced force fluctuations.

Maintaining pressure above a critical level is essential for successful ground state cooling.

Abstract

Counterintuitively, experiments show that an electromagnetically levitated particle escapes from its trap when the ambient pressure is reduced below a certain level even if the particle's motion is cooled by a resonator-based or feedback-based mechanism. Here, we theoretically show that the ambient pressure must be kept well above a critical value arising from gradient force fluctuations (viz., fluctuations in part of the EM force whose Hamiltonian is quadratic in the position of the particle). Also, we consider other force fluctuations, and determine whether different realizations of feedback cooling are able to reach the ground state. In some realizations, the cooling rate must be kept well below a critical value arising from feedback-induced gradient force fluctuations.