Sensitive microwave detectors are essential in radioastronomy1, dark-matter axion searches2 and superconducting quantum information science3,4. The conventional strategy to obtain higher-sensitivity bolometry is the nanofabrication of ever smaller devices to augment the thermal response5-7. However, it is difficult to obtain efficient photon coupling and to maintain the material properties in a device with a large surface-to-volume ratio owing to surface contamination. Here we present an ultimately thin bolometric sensor based on monolayer graphene. To utilize the minute electronic specific heat and thermal conductivity of graphene, we develop a superconductor-graphene-superconductor Josephson junction8-13 bolometer embedded in a microwave resonator with a resonance frequency of 7.9 gigahertz and over 99 per cent coupling efficiency. The dependence of the Josephson switching current on the operating temperature, charge density, input power and frequency shows a noise-equivalent power of 7 × 10-19 watts per square-root hertz, which corresponds to an energy resolution of a single 32-gigahertz photon14, reaching the fundamental limit imposed by intrinsic thermal fluctuations at 0.19 kelvin. Our results establish that two-dimensional materials could enable the development of bolometers with the highest sensitivity allowed by the laws of thermodynamics.

中文翻译：

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基于石墨烯的约瑟夫森结微波辐射热计

灵敏的微波探测器在射电天文学 1、暗物质轴子搜索 2 和超导量子信息科学 3、4 中必不可少。获得更高灵敏度的辐射热测定法的传统策略是对更小的设备进行纳米制造，以增强热响应 5-7。然而，由于表面污染，在具有大表面体积比的器件中难以获得有效的光子耦合并保持材料特性。在这里，我们提出了一种基于单层石墨烯的最终薄热传感器。为了利用石墨烯的微小电子比热和热导率，我们开发了一种嵌入微波谐振器中的超导体-石墨烯-超导体约瑟夫森结 8-13 辐射热计，其谐振频率为 7.9 GHz，耦合效率超过 99%。约瑟夫森开关电流对工作温度、电荷密度、输入功率和频率的依赖性表明噪声等效功率为 7 × 10-19 瓦/平方根赫兹，对应于单个 32 GHz 的能量分辨率photon14，达到了 0.19 开尔文的固有热波动所施加的基本极限。我们的结果表明，二维材料可以开发热力学定律允许的具有最高灵敏度的辐射热计。达到 0.19 开尔文的固有热波动所施加的基本极限。我们的结果表明，二维材料可以开发热力学定律允许的具有最高灵敏度的辐射热计。达到 0.19 开尔文的固有热波动所施加的基本极限。我们的结果表明，二维材料可以开发热力学定律允许的具有最高灵敏度的辐射热计。