Quenching decoherence sources of solid-state quantum systems by interaction with quantum liquids.

Quantum entanglement is the key resource of quantum mechanics; its use is going to open a way to powerful computing and advanced sensing.

Yet, an uncontrolled entanglement with parasitic degrees of freedom in the environment kills the quantum advantage, causing decoherence of quantum state. We focus on engineered superconducting solid-state quantum systems.

They are made by nanofabrication, which typically leaves some non-crystalline fabrication debris; the tunnel junction itself is made of amorphous alumina.

Therefore, the sources of decoherence in superconducting circuits are intimately related to the physics of amorphous materials, hosting a plethora of two-level fluctuators and stray spins; both providing 1/f noise, detrimental for the qubit. Interaction of decohering environment with quantum devices is temperature dependent.

Recently, we cooled down the superconducting device to submillikelvin temperatures by immersing it in a quantum liquid 3He, observing the first-ever thermalization of decohering bath down to 1 mK and the reduction of 1/f noise in the superconducting resonator. Thus, we confirmed a strong interaction of quantum liquid with the decohering bath.

Here we aim at extending the experiment with resonator towards pulsed measurements of superconducting qubits, scrutinizing and optimizing the silencing effect of quantum liquid in the qubit decohering environment, aiming at eliminating its detrimental effect on a qubit, regardless of microscopic defects nature.