The major task of detecting axions or axion-like particles has two challenges. On the one hand, the ultimate sensitivity is required, down to the energy of a single microwave photon of the yoctojoule range. On the other hand, since the detected events are supposed to be rare, the dark count rate of the detector must be extremely low. We show that this trade-off can be approached due to the peculiar switching dynamics of an underdamped Josephson junction in the phase diffusion regime. The detection of a few photons’ energy at 10 GHz with dark count time above 10 s and the efficiency close to unity was demonstrated. Further enhancements require a detailed investigation of the junction switching dynamics.

检测轴子或类轴子粒子的主要任务有两个挑战。一方面，需要最终的灵敏度，低至 yoctojoule 范围内的单个微波光子的能量。另一方面，由于检测到的事件应该是罕见的，所以检测器的暗计数率必须极低。我们表明，由于相扩散状态中欠阻尼约瑟夫森结的特殊开关动力学，可以实现这种权衡。证明了在 10 GHz 下检测到几个光子的能量，暗计数时间超过 10 s，效率接近 1。进一步的增强需要对结开关动态进行详细调查。