Bench-Top Cooling of a Microwave Mode Using an Optically Pumped Spin Refrigerator

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