We demonstrate nondestructive (lossless) fluorescent state detection of individual neutral atom qubits trapped in an optical lattice. The hyperfine state of the atom is measured with a 95% accuracy and an atom loss rate of 1%. Individual atoms are initialized and detected over 100 times before being lost from the trap, representing a 100-fold improvement in data collection rates over previous experiments. Microwave Rabi oscillations are observed with repeated measurements of one and the same single atom.

We measure the AC-Stark shifts of the 5S 1/2 , F = 2 → 5P 3/2 , F = 3 transitions of individual optically trapped 87 Rb atoms using a non-destructive detection technique that allows us to measure the fluorescent signal of one-and-the-same atom for over 60 seconds. These measurements allow efficient and rapid characterization of single atom traps that is required for many coherent quantum information protocols. Although this method is demonstrated using a single atom trap, the concept is readily extended to resolvable atomic arrays. PACS numbers: 32.60.+i, 32.70.Jz, 37.10.Gh Optical dipole trapping of individual neutral atoms is an active area of research, motivated in large part by applications in quantum information science, quantum many-body physics, and investigations of foundational issues in quantum mechanics. Building upon the early demonstrations of single neutral atom traps [1,2], there have been many impressive advances with resolved atom traps including deterministic loading [3], manipulation and control of single atoms [4], cooling [5,6], non-destructive state measurement [7,8], multidimensional atomic registers [9][10][11][12], cavity QED with individual trapped atoms [13][14][15] and demonstration of atom-photon [16,17] and atom-atom entanglement [18][19][20][21]. Resolved atom optical dipole traps can be used to hold cold atoms for times exceeding 300 s [22] and provide a promising alternative to rf trapped ion systems. However, one important difference compared with rf ion traps is that the optical trapping fields intrinsically shift the energy levels of the atoms (so-called 'light shifts') and thereby alter both the energy levels in which the information is stored (typically ground state hyperfine levels) as well as the frequencies of the optical transitions needed to manipulate the atoms. Successful realization of large-scale neutral atom quantum registers will require measurements of these shifts for each individual atom in order to characterize the trapping environments. A variety of destructive techniques (in the sense that the trapped atom is lost) have been used to measure excited state AC-Stark shifts of trapped neutral atoms including trap ejection excitation techniques [23], absorption spectra of singly trapped 87 Rb atoms [24] and ionization from Rydberg states [25,26]. For practical purposes, it will be necessary to employ non-destructive techniques for arrays of more than a few atoms.The focus of this work is the development of an efficient technique to characterize the transition shifts for the typical case in which the differential shifts of the excited states are comparable to both the intrinsic linewidth of the transition and the shifts of the ground state. The principle novelty of our method is that it is nondestructive in the sense that a single atom can be used to obtain the fluorescent spectrum of entire excited state manifold. It employs a continuous stream of short alternating probe and cooling pulses (durations 1 µs and 99 µs respectively) together with gated single-pho...

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