# Elimination of Thermomechanical Noise in Piezoelectric Optomechanical Crystals

## TL;DR

This paper demonstrates the elimination of thermomechanical noise in a GHz-frequency piezoelectric optomechanical crystal by cryogenic cooling, achieving near-ground-state occupancy and enabling low-noise quantum transduction.

## Contribution

It introduces a method to eliminate thermomechanical noise in mechanical modes of optomechanical crystals using cryogenic cooling, advancing quantum information applications.

## Key findings

- Mechanical mode occupancy reduced to 0.7 phonons
- Cryogenic cooling effectively suppresses thermal noise
- Path established for low-noise quantum transduction

## Abstract

Mechanical modes are a potentially useful resource for quantum information applications, such as quantum-level wavelength transducers, due to their ability to interact with electromagnetic radiation across the spectrum. A significant challenge for wavelength transducers is thermomechanical noise in the mechanical mode, which pollutes the transduced signal with thermal states. In this paper, we eliminate thermomechanical noise in the GHz-frequency mechanical breathing mode of a piezoelectric optomechanical crystal using cryogenic cooling in a dilution refrigerator. We optically measure an average thermal occupancy of the mechanical mode of only $0.7\pm0.4 ~ \mathrm{phonons}$, providing a path towards low-noise microwave-to-optical conversion in the quantum regime.