Cavity-mediated rapid state detection of single atoms in tweezer arrays

The ability to measure a subset of a quantum system without perturbing the rest paves the way for quantum error correction, quantum teleportation, and other real-time feedback processes. Here, we demonstrate rapid, localized, and lossless state measurement of single ⁸⁷Rb atoms in an optical tweezer array adjacent to a high-finesse optical cavity. This extends the capabilities of atomic array experiments by offering an alternative to global detection relying on state-selective atom loss and fluorescence imaging. In our work, single atoms are moved into the cavity for fast fluorescence- or transmission-based readout that differentiates among the ground state hyperfine levels and empty cavity. We achieve measurement fidelities exceeding 99% in timescales of tens of microseconds. To establish the local nature of this measurement, we initialize a two-atom array and perform a microwave Ramsey experiment, with a cavity measurement of the first atom between Ramsey pulses on the second atom. The second atom’s coherence is unperturbed by the first atom measurement.