A phonon laser in the quantum regime

TL;DR

This paper demonstrates a quantum-regime phonon laser using a trapped-ion system with controlled dissipation and coupling, achieving phase locking and observing phase diffusion near the ground state.

Contribution

It introduces a trapped-ion setup that operates as a phonon laser close to the quantum ground state with controllable dissipation channels.

Findings

Achieved phonon laser operation with average phonon number <10.

Demonstrated phase locking of the oscillator to an external drive.

Observed phase diffusion through quantum state reconstruction.

Abstract

We demonstrate a trapped-ion system with two competing dissipation channels, implemented independently on two ion species co-trapped in a Paul trap. By controlling coherent spin-oscillator couplings and optical pumping rates we explore the phase diagram of this system, which exhibits a regime analogous to that of a (phonon) laser but operates close to the quantum ground state with an average phonon number of $\bar{n}<10$. We demonstrate phase locking of the oscillator to an additional resonant drive, and also observe the phase diffusion of the resulting state under dissipation by reconstructing the quantum state from a measurement of the characteristic function.