Phonon counting thermometry of an ultracoherent membrane resonator near its motional ground state

TL;DR

This paper demonstrates phonon counting thermometry and quantum state detection of a near-ground-state mechanical oscillator, enabling studies of non-Gaussian states in macroscopic objects with potential applications in quantum information.

Contribution

It introduces a technique for generating and detecting quantum states of mechanical motion via phonon counting near the ground state of a micromechanical oscillator.

Findings

Achieved phonon counting thermometry near the ground state with $ar{n}=0.23$ phonons.

Demonstrated detection of scattered photons using an ultra-narrowband optical filter.

Enabled studies of long-lived non-Gaussian motional states in heavy objects.

Abstract

Generation of non-Gaussian quantum states of macroscopic mechanical objects is key to a number of challenges in quantum information science, ranging from fundamental tests of decoherence to quantum communication and sensing. Heralded generation of single-phonon states of mechanical motion is an attractive way towards this goal, as it is, in principle, not limited by the object size. Here we demonstrate a technique which allows for generation and detection of a quantum state of motion by phonon counting measurements near the ground state of a 1.5 MHz micromechanical oscillator. We detect scattered photons from a membrane-in-the-middle optomechanical system using an ultra-narrowband optical filter, and perform Raman-ratio thermometry and second-order intensity interferometry near the motional ground state ($\bar{n}=0.23\pm0.02$ phonons). With an effective mass in the nanogram range, our system lends itself for studies of long-lived non-Gaussian motional states with some of the heaviest objects to date.