Millimeter-Wave Four-Wave Mixing via Kinetic Inductance for Quantum Devices

Abstract

Millimeter-wave superconducting devices offer a platform for quantum experiments at temperatures above 1 K, and new avenues for studying light-matter interactions in the strong coupling regime. Using the intrinsic nonlinearity associated with kinetic inductance of thin film materials, we realize four-wave mixing at millimeter-wave frequencies, demonstrating a key component for superconducting quantum systems. We report on the performance of niobium nitride resonators around 100 GHz, patterned on thin (20-50 nm) films grown by atomic layer deposition, with sheet inductances up to 212 pH/ and critical temperatures up to 13.9 K. For films thicker than 20 nm, we measure quality factors from 1-6×10 4 , likely limited by two-level systems. Finally we measure degenerate parametric conversion for a 95 GHz device with a forward efficiency up to +16 dB, paving the way for the development of nonlinear quantum devices at millimeter-wave frequencies.For superconducting quantum circuits, the millimeterwave spectrum presents a fascinating frequency regime between microwaves and optics, giving access to a wider range of energy scales, and lower sensitivity to thermal background noise due to higher photon energies. Many advances have been made refining microwave quantum devices [1,2], typically relying on ultra-low temperatures in the millikelvin range to reduce sources of noise and quantum decoherence. Using millimeter-wave photons as building blocks for superconducting quantum devices offers transformative opportunities by allowing quantum experiments to be run at liquid Helium-4 temperatures, allowing higher device power dissipation and enabling large scale direct integration with semiconductor devices [2]. Millimeter-wave quantum devices could also provide new routes for studying strong-coupling light-matter interactions in this frequency regime [3][4][5][6][7], and present new opportunities for quantum-limited frequency conversion and detection [8,9].Recent interest in next-generation communication devices [10, 11] has led to important advances in sensitive millimeter-wave measurement technology around 100 GHz. Realizing quantum systems at these frequencies however requires both the demonstration of lowloss components -device materials with low absorption rates [12][13][14] and resonators with long photon lifetimes [15-20] -and most importantly, elements providing nonlinear interactions, which for circuit quantum optics can be realized with four-wave mixing Kerr terms in the Hamiltonian. One approach commonly used at microwave frequencies relies on aluminum Josephson junctions [2], which yield necessary four-wave mixing at low powers. However to avoid breaking Cooper pairs with high-frequency photons, devices at millimeter-wave frequencies are limited to materials with higher superconducting critical temperatures (T c ). Higher T c junctions have been implemented as high-frequency mixers for millimeter-wave detection [9,21,22], and ongoing efforts are improving losses for quantum applications [23,24].Kinetic inductance (KI)...

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