A tunable high-Q millimeter wave cavity for hybrid circuit and cavity QED experiments

Abstract

The millimeter wave (mm-wave) frequency band provides exciting prospects for quantum science and devices, since many high-fidelity quantum emitters, including Rydberg atoms, molecules and silicon vacancies, exhibit resonances near 100 GHz. High-Q resonators at these frequencies would give access to strong interactions between emitters and single photons, leading to rich and unexplored quantum phenomena at temperatures above 1K. We report a 3D mmwave cavity with a measured single-photon internal quality factor of 3×10 7 and mode volume of 0.14×λ 3 at 98.2 GHz, sufficient to reach strong coupling in a Rydberg cavity QED system. An in-situ piezo tunability of 18 MHz facilitates coupling to specific atomic transitions. Our unique, seamless and optically accessible resonator design is enabled by the realization that intersections of 3D waveguides support tightly confined bound states below the waveguide cutoff frequency. Harnessing the features of our cavity design, we realize a hybrid mm-wave and optical cavity, designed for interconversion and entanglement of mm-wave and optical photons using Rydberg atoms. chemical sensing and effective medical diagnostics 25,26 . Recently, the search for higher bandwidth and lower latency communication brought mm-wave wave frequencies into the focus of the telecommunication industry 27,28 . Once prohibitively limited and expensive, mm-wave technology is be-arXiv:1911.00553v1 [quant-ph] 1 Nov 2019 109 GHz 98 GHz 92 GHz 30 GHz a. b. c. d. e.

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