Matter Wave Interferometry of a Levitated Thermal Nano-Oscillator Induced and Probed by a Spin

TL;DR

This paper demonstrates a method to observe matter wave interference in a levitated nano-oscillator by coupling it to a spin and using Ramsey interferometry, enabling coherence detection without complex controls.

Contribution

It introduces a spin-based interferometry scheme for thermal nano-oscillators that avoids the need for cavities or spatial detection, simplifying quantum coherence experiments.

Findings

Successful coupling of spin and motion in a levitated diamond bead.

Evidence of matter wave interference in a thermal nano-oscillator.

Coherence detection via gravitational phase differences.

Abstract

We show how the interference between spatially separated states of the center of mass (COM) of a mesoscopic harmonic oscillator can be evidenced by coupling it to a spin and performing solely spin manipulations and measurements (Ramsey Interferometry). We propose to use an optically levitated diamond bead containing an NV center spin. The nano-scale size of the bead makes the motional decoherence due to levitation negligible. The form of the spin-motion coupling ensures that the scheme works for thermal states so that moderate feedback cooling suffices. No separate control or observation of the COM state is required and thereby one dispenses with cavities, spatially resolved detection and low mass-dispersion ensembles. The controllable relative phase in the Ramsey interferometry stems from a gravitational potential difference so that it uniquely evidences coherence between states which involve the whole nano-crystal being in spatially distinct locations.