Much of modern metrology and communication technology encodes information in electromagnetic waves, typically as an amplitude or phase. Although current hardware can perform near-ideal measurements of photon number or field amplitude, the ability to perform an ideal phase measurement is still lacking, even in principle. In this work, we implement a single-shot canonical phase measurement on a one-photon wave packet, which surpasses the current standard of heterodyne detection and is optimal for single-shot phase estimation. By applying quantum feedback to a Josephson parametric amplifier, our system adaptively changes its measurement basis during photon arrival and allows us to validate the detector’s performance by tracking the quantum state of the photon source. These results demonstrate that quantum feedback can both enhance the precision of a detector and enable it to measure new classes of physical observables.

许多现代计量和通信技术通常将电磁波中的信息编码为幅度或相位。尽管当前的硬件可以执行光子数或场振幅的近乎理想的测量，但即使在原理上仍缺乏执行理想相位测量的能力。在这项工作中，我们在单光子波包上实现了单脉冲规范相位测量，这超过了当前的外差检测标准，是单脉冲相位估计的最佳选择。通过将量子反馈应用于约瑟夫森参数放大器，我们的系统在光子到达期间自适应地改变其测量基础，并允许我们通过跟踪光子源的量子状态来验证探测器的性能。