Abstract
We achieve fast, nondestructive quantum-state readout via fluorescence detection of a single Rb atom in the 5 () 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 in a readout time of s with the atom retained in of the trials, representing an advancement over other magnetic-state-insensitive techniques. We demonstrate that the 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.