Spectroscopy and Thermometry of Drumhead Modes in a Mesoscopic Trapped-Ion Crystal using Entanglement

TL;DR

This paper demonstrates a method to perform spectroscopy and thermometry on individual motional modes in a large 2D ion crystal using entanglement-induced decoherence, enabling precise measurement of drumhead modes.

Contribution

It introduces a novel technique leveraging entanglement to transduce and measure complex motional modes in a mesoscopic ion crystal with high spatial resolution.

Findings

Successful excitation of arbitrary transverse modes in a 2D ion crystal.

Detection of sub-nanometer displacements via entanglement.

Characterization of drumhead mode spectra in a large ion array.

Abstract

We demonstrate spectroscopy and thermometry of individual motional modes in a mesoscopic 2D ion array using entanglement-induced decoherence as a method of transduction. Our system is a $\sim$400 $\mu$m-diameter planar crystal of several hundred $^9$Be$^+$ ions exhibiting complex drumhead modes in the confining potential of a Penning trap. Exploiting precise control over the $^9$Be$^+$ valence electron spins, we apply a homogeneous spin-dependent optical dipole force to excite arbitrary transverse modes with an effective wavelength approaching the interparticle spacing ($\sim$20 \nolinebreak$\mu$m). Center-of-mass displacements below 1 nm are detected via entanglement of spin and motional degrees of freedom.