Single photon detection is a key resource for sensing at the quantum limit and the enabling technology for measurement-based quantum computing. Photon detection at optical frequencies relies on irreversible photoassisted ionization of various natural materials. However, microwave photons have energies 5 orders of magnitude lower than optical photons, and are therefore ineffective at triggering measurable phenomena at macroscopic scales. Here, we report the observation of a new type of interaction between a single two-level system (qubit) and a microwave resonator. These two quantum systems do not interact coherently; instead, they share a common dissipative mechanism to a cold bath: the qubit irreversibly switches to its excited state if and only if a photon enters the resonator. We have used this highly correlated dissipation mechanism to detect itinerant photons impinging on the resonator. This scheme does not require any prior knowledge of the photon waveform nor its arrival time, and dominant decoherence mechanisms do not trigger spurious detection events (dark counts). We demonstrate a detection efficiency of 58% and a record low dark count rate of 1.4 per millisecond. This work establishes engineered nonlinear dissipation as a key enabling resource for a new class of low-noise nonlinear microwave detectors.

中文翻译：

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不可逆量子比特光子耦合用于巡回微波光子的检测

单光子检测是在量子极限进行传感的关键资源，也是基于测量的量子计算的使能技术。光学频率下的光子检测依赖于各种天然材料的不可逆光辅助电离。但是，微波光子的能量比光学光子低5个数量级，因此在宏观尺度上无法有效触发可测量的现象。在这里，我们报告了对单个二级系统（qubit）和微波谐振器之间新型相互作用的观察。这两个量子系统没有相干相互作用。取而代之的是，它们对冷水浴具有共同的耗散机制：当且仅当光子进入谐振器时，量子位才能不可逆地切换到其激发态。我们已经使用这种高度相关的耗散机制来检测撞击在谐振器上的流动光子。该方案不需要光子波形的任何先验知识或其到达时间，并且主要的去相干机制不会触发虚假检测事件（暗计数）。我们证明了58％的检测效率和创纪录的1.4毫秒的低暗计数率。这项工作将工程非线性耗散确立为新型低噪声非线性微波探测器的关键支持资源。每毫秒4个。这项工作将工程非线性耗散确立为新型低噪声非线性微波探测器的关键支持资源。每毫秒4个。这项工作将工程非线性耗散确立为新型低噪声非线性微波探测器的关键支持资源。