Midcircuit Measurements on a Single-Species Neutral Alkali Atom Quantum Processor

We demonstrate midcircuit measurements in a neutral atom array by shelving data qubits in protected hyperfine-Zeeman substates while nondestructively measuring an ancilla qubit. Measurement fidelity is enhanced using microwave repumping of the ancilla during the measurement. The coherence of the shelved data qubits is extended during the ancilla readout with dynamical decoupling pulses, after which the data qubits are returned to mf=0 computational basis states. We demonstrate that the quantum state of the data qubits is well preserved up to a constant phase shift with a state preparation and measurement–corrected process fidelity of F = 97.0(5)%. The measurement fidelities on the ancilla qubit after correction for state preparation errors are F = 94.9(8)% and F = 95.3(1.1)% for |0> and |1> qubit states, respectively. We discuss extending this technique to repetitive quantum error correction using quadrupole recooling and microwave-based quantum-state resetting.