Sub-ms, nondestructive, time-resolved quantum-state readout of a single, trapped neutral atom

We achieve fast, nondestructive quantum-state readout via fluorescence detection of a single ⁸⁷Rb atom in the 5S_1/2 $F=2$ ground state held in an optical dipole trap. The atom is driven by linearly-polarized readout laser beams, making the scheme insensitive to the distribution of atomic population in the magnetic sub-levels. We demonstrate a readout fidelity of 97.6pm0.2\% in a readout time of 160pm20 μs with the atom retained in >97\% of the trials, representing an advancement over other magnetic-state-insensitive techniques. We demonstrate that the F=2 state is partially protected from optical pumping by the distribution of the dipole matrix elements for the various transitions and the AC-Stark shifts from the optical trap. Our results are likely to find application in neutral-atom quantum computing and simulation.