Measurement-based ground state cooling of a trapped ion oscillator

TL;DR

This paper demonstrates a measurement-based cooling method for a trapped ion, achieving high-fidelity ground state preparation by heralding the ion's motional ground state, which could be applicable to other quantum systems.

Contribution

The authors experimentally implement a measurement-based cooling technique on a trapped ion, achieving over 95% heralding fidelity for ground state preparation.

Findings

Heralding fidelity exceeds 95%.

Effective ground state selection from a thermal state with mean excitation ~18.

Technique applicable to systems less amenable to laser cooling.

Abstract

Measurement-based cooling is a method by which a quantum system, initially in a thermal state, can be prepared in its ground state through some sort of measurement. This is done by making a measurement that heralds the system being in the desired state. Here we demonstrate the application of a measurement-based cooling technique to a trapped atomic ion. The ion is pre-cooled by Doppler laser cooling to a thermal state with a mean excitation of $\bar n \approx 18$ and the measurement-based cooling technique selects those occasions when the ion happens to be in the motional ground state. The fidelity of the heralding process is greater than 95%. This technique can be applied to other systems that are not as amenable to laser cooling as trapped ions.