High-fidelity simultaneous detection of a trapped-ion qubit register

Qubit state detection is an important part of a quantum computation. As the number of qubits in a quantum register increases, it is necessary to maintain high-fidelity detection to accurately measure the multiqubit state. Here we present experimental demonstration of high-fidelity detection of a multiqubit trapped-ion register with an average single-qubit detection error of 4.2(1.5) ppm and a four-qubit state detection error of 17(2) ppm, limited by the decay lifetime of the qubit, using a single-photon-sensitive camera with fast data collection, excellent temporal and spatial resolution, and low instrumental crosstalk.