Quantum bath suppression in a superconducting circuit by immersion cooling

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 $T\approx 50$ 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 ${}^3$He. 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 ${}^3$He 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.

References in corpus (12)

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Cited by in corpus (10)

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• Quasiparticle spectroscopy, transport, and magnetic properties of Nb films used in superconducting transmon qubits
• Feasibility of the Josephson voltage and current standards on a single chip
• Loss and decoherence in superconducting circuits on silicon: Insights from electron spin resonance
• Leveraging collective effects for thermometry in waveguide quantum electrodynamics
• Theory of Two-level Tunneling Systems in Superconductors
• Logarithmic light cone, slow entanglement growth, and quantum memory
• Dissipative evolution of a two-level system through a geometry-based classical mapping
• Photonic Simulation of Localization Phenomena Using Boson Sampling
• Hydrogen crystals reduce dissipation in superconducting resonators