Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: 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 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
narrow-band cryogenic load, removing photons from the otherwise
room-temperature mode via stimulated absorption. The noise temperature of the
microwave mode dropped to $50^{+18}_{-32}$ 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 K (corresponding to
$\sim$140 microwave photons). These observations, when combined with
engineering improvements to deepen the cooling, identify the system as a
narrow-band 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.

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The categories of this paper are: econ
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The categories of this paper are: atom-ph
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The categories of this paper are: chao-dyn
2
The categories of this paper are: math
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The categories of this paper are: alg-geom
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The categories of this paper are: eess
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The categories of this paper are: hep-lat
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The categories of this paper are: mtrl-th
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The categories of this paper are: q-bio
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The categories of this paper are: ao-sci
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The categories of this paper are: solv-int
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The categories of this paper are: acc-phys
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The categories of this paper are: q-alg
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The categories of this paper are: nucl-ex
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The categories of this paper are: gr-qc
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The categories of this paper are: astro-ph