Measuring the state of a qubit is a key fundamental operation of a quantum computer. High-fidelity single-shot readout of superconducting qubits can be achieved using parametric amplifiers at millikelvin temperatures. However, scaling parametric amplifiers beyond hundreds of qubits is challenging due to practical size and power limitations. Nanobolometers can, in contrast, offer scalability, sensitivity and speed suitable for qubit readout. Here we show that a bolometer can provide single-shot qubit readout with a readout duration of 13.9 μs and a single-shot fidelity of 0.618. The fidelity is mainly limited by the energy relaxation time of the qubit (28 μs), and a fidelity of 0.927 is found after removing errors arising from this relaxation. In the future, higher-fidelity single-shot readout may be achieved through improvements in chip design and experimental setup, as well as a change in the bolometer absorber material to reduce the readout time to the level of hundreds of nanoseconds and below.

测量量子位的状态是量子计算机的关键基本操作。使用参数放大器可以在毫开尔文温度下实现超导量子位的高保真单次读出。然而，由于实际尺寸和功率限制，将参数放大器扩展到数百个量子位以上具有挑战性。相比之下，纳米测辐射热计可以提供适合量子位读出的可扩展性、灵敏度和速度。在这里，我们展示了测辐射热计可以提供单次量子位读数，读出持续时间为 13.9 μs，单次保真度为 0.618。保真度主要受到量子位的能量弛豫时间（28 μs）的限制，消除该弛豫产生的误差后，保真度为 0.927。未来，可以通过芯片设计和实验装置的改进以及辐射热测量计吸收材料的改变来实现更高保真度的单次读出，以将读出时间减少到数百纳秒及以下的水平。