Stern-Gerlach detection of neutral atom qubits in a state dependent optical lattice

We demonstrate qubit state measurement for ~160 Cesium atoms in a 3D optical lattice based on coherent spatial splitting of the atoms' wavefunctions. The measurement fidelity is 0.9994, essentially independent of the number of qubits measured. The detection scheme is reminiscent of the Stern-Gerlach experiment, but carried out in light traps. The measurement causes no loss, which allows us to demonstrate re-initialization of the 3D qubit array after state measurement, including the replacement of an atom lost to a background gas collision.