Abstract
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.
Highlights
Qubits used in quantum computing suffer from errors, either from the qubit interacting with the environment, or from imperfect quantum logic gates
Superconducting nanowire single photon detectors (SNSPDs) have become the ubiquitous technology for photon counting applications because of their nearly ideal performance metrics. These detectors have high detection efficiency, low dark count rates, and high maximum count rates[17]. These superb performance characteristics compared to other single-photon detectors have made possible recent experimental demonstrations utilizing single photons such as a loophole-free Bell inequality test[18], Lunar Laser Communication Demonstration[19], high-rate quantum key distribution[20], as well as providing an alternative solution to photomultiplier tubes (PMTs) and chargecoupled devices (CCDs) for the detection of photons scattered by trapped ions
It is critical to preserve the memory of the data qubits while this resonant, destructive detection process is performed on the ancilla qubits
Summary
Qubits used in quantum computing suffer from errors, either from the qubit interacting with the environment, or from imperfect quantum logic gates. In most atomic qubits where resonant fluorescence is used for state detection, the scattered photons from the pump beam or the atoms can cause decoherence in nearby qubits by the same statedependent fluorescence process used for qubit state detection Certain quantum circuits, such as quantum error correction, require that ancilla qubits be measured in the middle of the algorithm[21,22]. One approach is to transfer the ancilla qubit into a different ion species and detect it using light at a different wavelength, so the pump beam does not affect the data qubits[23,24] Another approach is to leverage the segmented control electrodes of microfabricated surface traps to create multiple trapping zones[25,26], and spatially separate the ancilla qubits from the data qubits for the state detection process[27].
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