We experimentally demonstrate the temporary removal of thermal photons from a microwave mode at 1.45 GHz through its interaction with the spin-polarized triplet states of photo-excited pentacene molecules doped within a $p$-terphenyl crystal at room temperature. The crystal functions electromagnetically as a narrowband cryogenic load, removing photons from the otherwise room-temperature mode via stimulated absorption. The noise temperature of the microwave mode dropped to ${50}_{-32}^{+18}\mathrm{K}$ (as directly inferred by noise-power measurements), while the metal walls of the cavity enclosing the mode remained at room temperature. Simulations based on the same system’s behavior as a maser (which could be characterized more accurately) indicate the possibility of the mode’s temperature sinking to $\sim 10\mathrm{K}$ (corresponding to $\sim 140$ microwave photons). These observations, when combined with engineering improvements to deepen the cooling, identify the system as a narrowband yet extremely convenient platform—free of cryogenics, vacuum chambers, and strong magnets—for realizing low-noise detectors, quantum memory, and quantum-enhanced machines (such as heat engines) based on strong spin-photon coupling and entanglement at microwave frequencies.

中文翻译：

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使用光泵自旋冰箱对微波模式进行台式冷却

我们通过实验证明了在 1.45 GHz 的微波模式下通过其与掺杂在 $磷$-三联苯晶体在室温下。该晶体在电磁方面起到窄带低温负载的作用，通过受激吸收从其他室温模式中去除光子。微波模式的噪声温度降至${50}_{-32}^{+18}\mathrm{钾}$（通过噪声功率测量直接推断），而封闭模式的腔体金属壁保持在室温。基于与脉泽相同的系统行为（可以更准确地表征）的模拟表明该模式的温度下降到$～10\mathrm{钾}$ （对应于 $～140$微波光子）。这些观察结果与深化冷却的工程改进相结合，确定该系统是一个窄带但极其方便的平台——没有低温、真空室和强磁铁——用于实现低噪声探测器、量子存储器和量子增强机器（例如热机）基于微波频率下的强自旋光子耦合和纠缠。