Demonstration of a circuit-QED maser based on a nanowire Josephson junction*

On-chip coherent microwave generation can be achieved by strongly coupling a dc biased Josephson junction to a high quality factor superconducting cavity [1]. The incorporation of a gate-tunable semiconducting nanowire Josephson junction in such a device enables fast control of the junction-cavity coupling and laser emission, paving the way for efficient scalable on-chip microwave control of superconducting qubits.
In these devices, the efficient down-conversion at higher order harmonics stimulates the creation of multiple coherent photons with a single Cooper pair tunneling event, increasing the phase coherence. However, performance is currently limited by incoherent dissipative processes such as quasiparticle poisoning (QPP) that suppress the laser coherence.
Here we report on the quenching of the coherence above the 4th order harmonic. We track the emission dynamics of the 5th order harmonic in time and observe emission blinking due to QPP events with characteristic timescales T_poisoning = 200 ± 10 μs and T_unpoisoning = 17 ± 2 μs.

Reference:
[1] M.C. Cassidy et al., Science 355, 939 (2017)