Shot-to-shot displacement noise in state-expansion protocols with inverted potentials

Abstract

Optically levitated nanoparticles are promising candidates for the generation of macroscopic quantum states of mechanical motion. Protocols to generate such states expose the particle to a succession of different potentials. Limited reproducibility of the alignment of these potentials across experimental realizations introduces additional noise. Here, we experimentally investigate and model how such shot-to-shot noise limits the coherence length of a levitated nanoparticle during a state-expansion protocol using a dark, inverted electrical potential. We identify electric stray fields and mechanical instabilities as major sources of shot-to-shot fluctuations. We discuss the resulting experimental requirements for state expansion protocols exploiting inverted potentials.