High-speed low-crosstalk detection of a 171 Yb + qubit using superconducting nanowire single photon detectors

Qubits used in quantum computing suffer from errors, either from the qubit interacting with the environment, or from imperfect quantum logic gates. Effective quantum error correcting codes require a high fidelity readout of ancilla qubits from which the error syndrome can be determined without affecting data qubits. Here, we present a detection scheme for 171Yb+ qubits, where we use superconducting nanowire single photon detectors and utilize photon time-of-arrival statistics to improve the fidelity and speed. Qubit shuttling allows for creating a separate detection region where an ancilla qubit can be measured without disrupting a data qubit. We achieve an average qubit state detection time of 11 μs with a fidelity of 99.931(6). The detection crosstalk error, defined as the probability that the data qubit coherence is lost due to the process of detecting an ancilla qubit, is reduced to ~2 × 10−5 by creating a separation of 370 μm between them. Trapped ions have gained momentum as a platform for quantum computing thanks to the ability of storing qubits in stable electron states of each ions and transfer of information among the ion qubits in the trap. The authors present an experimental scheme to detect trapped 171-ytterbium ion qubits using photon statistics and superconducting nanowire single photon detectors and report a qubit detection fidelity of 99.93% within 11 microseconds.