Radiation sensors based on the heating effect of absorbed radiation are typically simple to operate and flexible in terms of input frequency, so they are widely used in gas detection1, security2, terahertz imaging3, astrophysical observations4 and medical applications5. Several important applications are currently emerging from quantum technology and especially from electrical circuits that behave quantum mechanically, that is, circuit quantum electrodynamics6. This field has given rise to single-photon microwave detectors7-9 and a quantum computer that is superior to classical supercomputers for certain tasks10. Thermal sensors hold potential for enhancing such devices because they do not add quantum noise and they are smaller, simpler and consume about six orders of magnitude less power than the frequently used travelling-wave parametric amplifiers11. However, despite great progress in the speed12 and noise levels13 of thermal sensors, no bolometer has previously met the threshold for circuit quantum electrodynamics, which lies at a time constant of a few hundred nanoseconds and a simultaneous energy resolution of the order of 10h gigahertz (where h is the Planck constant). Here we experimentally demonstrate a bolometer that operates at this threshold, with a noise-equivalent power of 30 zeptowatts per square-root hertz, comparable to the lowest value reported so far13, at a thermal time constant two orders of magnitude shorter, at 500 nanoseconds. Both of these values are measured directly on the same device, giving an accurate estimation of 30h gigahertz for the calorimetric energy resolution. These improvements stem from the use of a graphene monolayer with extremely low specific heat14 as the active material. The minimum observed time constant of 200 nanoseconds is well below the dephasing times of roughly 100 microseconds reported for superconducting qubits15 and matches the timescales of currently used readout schemes16,17, thus enabling circuit quantum electrodynamics applications for bolometers.

中文翻译：

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在电路量子电动力学阈值下运行的辐射热计

基于吸收辐射的加热效应的辐射传感器通常操作简单，输入频率灵活，因此广泛应用于气体检测1、安全2、太赫兹成像3、天体物理观测4和医疗应用5。目前，量子技术，特别是具有量子力学行为的电路，即电路量子电动力学，正在出现一些重要的应用。该领域催生了单光子微波探测器 7-9 和在某些任务上优于经典超级计算机的量子计算机 10。热传感器具有增强此类设备的潜力，因为它们不会增加量子噪声并且它们更小，比常用的行波参量放大器更简单，功耗低约六个数量级。然而，尽管热传感器的速度 12 和噪声水平 13 取得了很大进步，但以前没有一个辐射热计达到电路量子电动力学的阈值，其时间常数为几百纳秒，同时能量分辨率为 10 赫吉赫兹量级（其中 h 是普朗克常数）。在这里，我们通过实验演示了一个在此阈值下运行的辐射热计，其噪声等效功率为 30 zeptowatts/平方根赫兹，与迄今为止报告的最低值相当 13，热时间常数缩短了两个数量级，为 500 纳秒. 这两个值都是直接在同一设备上测量的，为量热能量分辨率提供了 30h 千兆赫的准确估计。这些改进源于使用具有极低比热的石墨烯单层作为活性材料。观察到的 200 纳秒的最小时间常数远低于报告的超导量子位 15 的相移时间大约 100 微秒，并且与当前使用的读出方案的时间尺度相匹配 16,17，从而使辐射热计的电路量子电动力学应用成为可能。