Spectroscopy and thermometry of drumhead modes in a mesoscopic trapped-ion crystal using entanglement

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 400 µm-diameter planar crystal of several hundred 9Be+ ions exhibiting complex drumhead modes in the confining potential of a Penning trap. Exploiting precise control over the 9Be+ 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 (20 µm). Center-of-mass displacements below 1 nm are detected via the entanglement of spin and motional degrees of freedom.