We propose a detector of microwave photons that can distinguish the vacuum state, one-photon state, and the states with two or more photons. Its operation is based on the two-photon transition in a biased Josephson junction and detection occurs when it switches from a superconducting to a normal state. We model the detector theoretically. The detector performs with more than 90% success probability in several microseconds. The working frequency can be set at the design stage in the range from about 1 to 20 GHz.

中文翻译：

---

超导检测器，最多可计数两个微波光子

我们提出了一种微波光子检测器，它可以区分真空状态，单光子状态以及具有两个或更多光子的状态。它的操作基于偏置的约瑟夫森结中的双光子跃迁，并且当其从超导状​​态切换到正常状态时会进行检测。我们在理论上对检测器建模。检测器在几微秒内的成功率超过90％。可以在设计阶段将工作频率设置为大约1至20 GHz。