Single-junction quantum-circuit refrigerator

We propose a quantum-circuit refrigerator (QCR) based on photon-assisted quasiparticle tunneling through single normal-metal–insulator–superconductor (NIS) junction. In contrast to previous studies with multiple junctions and an additional charge island for the QCR, we directly connect NIS junction inductively shunted electrode of superconducting microwave resonator making device immune low-frequency noise. At low characteristic impedance parameters relevant recent experiment, observe that semiclassical model reproduces bias voltage dependence QCR-induced damping rate frequency shift. For high impedances, derive Born–Markov master equation use it significant non-linearities in dissipation further demonstrate that, this regime, QCR can be used initialize linear into non-thermal state even absence any drive.