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

Hao Wu, Shamil Mirkhanov, Wern Ng, and Mark Oxborrow
Phys. Rev. Lett. 127, 053604 – Published 29 July 2021
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Abstract

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 5032+18K (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 10K (corresponding to 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.

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  • Received 31 March 2021
  • Accepted 4 June 2021

DOI:https://doi.org/10.1103/PhysRevLett.127.053604

© 2021 American Physical Society

Physics Subject Headings (PhySH)

Atomic, Molecular & OpticalCondensed Matter, Materials & Applied Physics

Authors & Affiliations

Hao Wu, Shamil Mirkhanov, Wern Ng, and Mark Oxborrow*

  • Department of Materials, Imperial College London, Exhibition Road, London SW7 2AZ, United Kingdom

  • *Corresponding author. m.oxborrow@imperial.ac.uk

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Issue

Vol. 127, Iss. 5 — 30 July 2021

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