Recent Developments in Quantum-Circuit Refrigeration

Abstract

We review the recent progress in direct active cooling of the quantum-electric degrees freedom in engineered circuits, or quantum-circuit refrigeration. In 2017, the invention of a quantum-circuit refrigerator (QCR) based on photon-assisted tunneling of quasiparticles through a normal-metal--insulator--superconductor junction inspired a series of experimental studies demonstrating the following main properties: (i) the direct-current (dc) bias voltage of the junction can change the QCR-induced damping rate of a superconducting microwave resonator by orders of magnitude and give rise to non-trivial Lamb shifts, (ii) the damping rate can be controlled in nanosecond time scales, and (iii) the dc bias can be replaced by a microwave excitation, the amplitude of which controls the induced damping rate. Theoretically, it is predicted that state-of-the-art superconducting resonators and qubits can be reset with an infidelity lower than $10^{-4}$ in tens of nanoseconds using experimentally feasible parameters. A QCR-equipped resonator has also been demonstrated as an incoherent photon source with an output temperature above one kelvin yet operating at millikelvin. This source has been used to calibrate cryogenic amplification chains. In the future, the QCR may be experimentally used to quickly reset superconducting qubits, and hence assist in the great challenge of building a practical quantum computer.

14 pages, 9 figures, submitted to Annalen der Physik (AdP) 19.11.2021

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Cited by in corpus (9)

• Single-junction quantum-circuit refrigerator
• Initial experimental results on a superconducting-qubit reset based on photon-assisted quasiparticle tunneling
• A quantum Stirling heat engine operating in finite time
• Applications of Superconductor-Normal Metal Interfaces
• Exceptional-point-assisted entanglement, squeezing, and reset in a chain of three superconducting resonators
• Non-Hermitian topological quantum states in a reservoir-engineered transmon chain
• Quantum circuit refrigerator based on quantum dots coupled to normal-metal and superconducting electrodes
• Proposal for an autonomous quantum heat engine
• Dissipation and noise in strongly driven Josephson junctions