Characterization of noise of a quantum harmonic oscillator is important for many experimental platforms. We experimentally demonstrate motional spin-locking spectroscopy, a method that allows us to directly measure the motional noise spectrum of a quantum harmonic oscillator. We measure motional noise of a single trapped ion in a frequency range from 200 Hz to 5 kHz with a power spectral density that resolves noise over two orders of magnitude. Coherent modulations in the oscillation frequency of the oscillator can be probed with a relative frequency sensitivity at the 10−6 level.
@article{arxiv.2510.08732,
title = {Spin-Locking Spectroscopy of Harmonic Motion},
author = {Florian Kranzl and Adria Rospars and Johannes Franke and Manoj K. Joshi and Rainer Blatt and Christian F. Roos},
journal= {arXiv preprint arXiv:2510.08732},
year = {2025}
}