Phys.org June 16, 2023
Quantum circuits interact with the environment via several temperature-dependent degrees of freedom. 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 reflected in the thermal state population of qubits and polarisation of surface spins. An international team of researchers (UK, Sweden, USA – industry) demonstrated how to remove this thermal constraint by operating a circuit immersed in liquid 3He. This allowed cooling tof he decohering environment of a superconducting resonator. They saw a continuous change in measured physical quantities down to previously unexplored sub-mK temperatures. The 3He acted as a heat sink which increased the energy relaxation rate of the quantum bath coupled to the circuit a thousand times, yet the suppressed bath did not introduce additional circuit losses or noise. The researchers concluded that quantum bath suppression can reduce decoherence in quantum circuits opening a route for both thermal and coherence management in quantum processors… read more. Open Access TECHNICAL ARTICLE
Immersion of a superconducting quantum circuit in liquid 3He. Credit: Nature Communications volume 14, Article number: 3522 (2023)