2022/08/18 by A. Pontin, Pontin, A., T. S. Monteiro +1 · 1 citation
Physics and Astronomy · #Experimental and Theoretical Physics Studies #FOS: Physical sciences #Mechanical and Optical Resonators #Quantum Electrodynamics and Casimir Effect #Quantum Physics (quant-ph)
paper · pdf · doi:10.48550/arxiv.2208.09065
openalex publication_date 2022/08/18 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
Levitated nanoparticles are being intensively investigated from two different perspectives: as a potential realisation of macroscopic quantum coherence; and as ultra-sensitive sensors of force, down to the zeptoNewton level, with a range of various applications, including the search for Dark Matter. A future aim is to merge these two strands, enabling the development of quantum-limited sensors. Here we propose that mechanical cross-correlation spectra Sxy(ω) offer new possibilities: once detector misalignment errors are minimised, the spectral shape of Sxy(ω) directly points out the orientation of an external stochastic force, offering something akin to a compass in the x-y plane. We analyse this for detection of microscopic gas currents, but any broad spectrum directed force will suffice, enabling straightforward investigation with laboratory test forces with or without cavities. For a cavity set-up, we analyse misalignment imprecisions between detectors and motional modes due to for example optical back-actions that mask the signature of the directed forces, and show how to suppress them. Near quantum regimes, we quantify the imprecision due to the x-y correlating effect of quantum shot noise imprecision.