Acceleration sensing with magnetically levitated oscillators above a superconductor

TL;DR

This paper demonstrates a magnetically levitated oscillator above a superconductor as a highly sensitive acceleration sensor, achieving sensitivities down to 3×10⁻¹⁵ g/√Hz under ideal conditions with feedback cooling.

Contribution

It introduces a stable, magnetically levitated oscillator system above a superconductor for ultrasensitive acceleration measurements, with experimental and theoretical sensitivity estimates.

Findings

Achieved a background noise level of ~10⁻¹⁰ m/√Hz at 30.75 Hz

Measured an acceleration sensitivity of 1.2±0.2×10⁻¹⁰ g/√Hz under current conditions

Projected potential sensitivity of 3×10⁻¹⁵ g/√Hz in ideal low-temperature, low-pressure environment

Abstract

We experimentally demonstrate stable trapping of a permanent magnet sphere above a lead superconductor, in vacuum pressures of $4 \times 10^{-8}$~mbar. The levitating magnet behaves as a harmonic oscillator, with frequencies in the 4-31~Hz range detected, and shows promise to be an ultrasensitive acceleration sensor. We directly apply an acceleration to the magnet with a current carrying wire, which we use to measure a background noise of $\sim 10^{-10} \ \text{m}/\sqrt{\text{Hz}}$ at 30.75~Hz frequency. With current experimental parameters, we find an acceleration sensitivity of $S_a^{1/2} = 1.2 \pm 0.2 \times 10^{-10} \ \text{g}/\sqrt{\text{Hz}}$, for a thermal noise limited system. By considering a 300~mK environment, at a background helium pressure of $1 \times 10^{-10}$~mbar, acceleration sensitivities of $S_a^{1/2} \sim 3 \times 10^{-15} \ \text{g}/\sqrt{\text{Hz}}$ could be possible with ideal conditions and vibration isolation. To feasibly measure with such a sensitivity, feedback cooling must be implemented.