Detectors of propagating microwave photons have recently been realized using superconducting circuits. However a number-resolved photocounter is still missing. In this article, we demonstrate a single-shot counter for propagating microwave photons that can resolve up to $3$ photons. It is based on a pumped Josephson Ring Modulator that can catch an arbitrary propagating mode by frequency conversion and store its quantum state in a stationary memory mode. A transmon qubit then counts the number of photons in the memory mode using a series of binary questions. Using measurement based feedback, the number of questions is minimal and scales logarithmically with the maximal number of photons. The detector features a detection efficiency of $0.96\pm 0.04$, and a dark count probability of $0.030\pm 0.002$ for an average dead time of . To maximize its performance, the device is first used as an waveform detector from which an optimal pump is computed and applied. Depending on the number of incoming photons, the detector succeeds with a probability that ranges from $56\%$ to $99\%$.

中文翻译：

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传播微波模式的数字解析光计数器

最近已经使用超导电路实现了传播微波光子的检测器。但是，仍然缺少数字解析的光计数器。在本文中，我们演示了用于传播微波光子的单脉冲计数器，它可以解析为$3$光子。它基于抽运的约瑟夫森环形调制器，该调制器可以通过频率转换捕获任意传播模式，并将其量子状态存储在固定存储模式下。然后，transmon量子位使用一系列二进制问题来计算存储模式下的光子数量。使用基于测量的反馈，问题的数量最少，并且光子数量最大时对数缩放。该检测器的检测效率为$0.96\pm 0.04$，并且暗计数概率为 $0.030\pm 0.002$平均死时间为。为了使其性能最大化，该设备首先用作波形检测器，从中可以计算并应用最佳泵。根据入射光子的数量，检测器成功的概率为$56％$ 至 $99％$。