Mid-circuit cavity measurement in a neutral atom array

TL;DR

This paper demonstrates a high-fidelity, rapid, and nondestructive mid-circuit measurement technique for neutral atom arrays using a strongly coupled optical cavity, advancing quantum error correction capabilities.

Contribution

It introduces a cavity-based measurement method that achieves fast, high-fidelity, and nondestructive readout of individual atoms in a neutral atom array.

Findings

Measurement time within tens of microseconds

State preparation and measurement infidelity around 0.5%

No observable decoherence on neighboring atoms during measurement

Abstract

Subsystem readout during a quantum process, or mid-circuit measurement, is crucial for error correction in quantum computation, simulation, and metrology. Ideal mid-circuit measurement should be faster than the decoherence of the system, high-fidelity, and nondestructive to the unmeasured qubits. Here, we use a strongly coupled optical cavity to read out the state of a single tweezer-trapped 87Rb atom within a small tweezer array. Measuring either atomic fluorescence or the transmission of light through the cavity, we detect both the presence and the state of an atom in the tweezer, within only tens of microseconds, with state preparation and measurement infidelities of roughly 0.5% and atom loss probabilities of around 1%. Using a two-tweezer system, we find measurement on one atom within the cavity causes no observable hyperfine-state decoherence on a second atom located tens of microns from the cavity volume. This high-fidelity mid-circuit readout method is a substantial step towards quantum error correction in neutral atom arrays.