Lucas, M; Danilov, A V; Levitin, L V; Jayaraman, A; Casey, A J; Faoro, L; Tzalenchuk, A Ya; Kubatkin, S E; Saunders, J; de Graaf, S E (2023) Quantum bath suppression in a superconducting circuit by immersion cooling. Nature Communications, 14. 3522

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Abstract

Quantum circuits interact with the environment via several temperature-dependent degrees of freedom. Yet, multiple experiments to-date have shown that most properties of superconducting devices appear to plateau out at T ≈ 50 mK -- far above the refrigerator base temperature.
This is for example reflected in the thermal state population of qubits, in excess numbers of quasiparticles, and polarisation of surface spins -- factors contributing to reduced coherence. We demonstrate how to remove this thermal constraint by operating a circuit immersed in liquid 3He. This allows to efficiently cool the decohering environment of a superconducting resonator, and we see a continuous change in measured physical quantities down to previously unexplored sub-mK temperatures. The 3He acts as a heat sink which increases the energy relaxation rate of the quantum bath coupled to the circuit a thousand times, yet the suppressed bath does not introduce additional circuit losses or noise. Such quantum bath suppression can reduce decoherence in quantum circuits and opens a route for both thermal and coherence management in quantum processors.

Item Type:	Article
Keywords:	Helium-3; immersion cooling; superconducting; resonator; material defects
Subjects:	Quantum Phenomena > Quantum Information Processing and Communication
Divisions:	Quantum Technologies
Identification number/DOI:	10.1038/s41467-023-39249-z
Last Modified:	18 Oct 2023 15:00
URI:	https://eprintspublications.npl.co.uk/id/eprint/9848