Behavior of Josephson travelling-wave parametric amplifier under strong drives

Amplifying weak microwave signals with a noise closed to the minimum imposed by quantum mechanics is now routinely done with superconducting quantum devices. Namely, Josephson-based Traveling Wave Parametric Amplifiers (JTWPA) have shown excellent broadband performance with added noise below 0.5 photons[1]. In this talk, we explore the case of small weak pulses generated through high power pulses.

Sending a train of such high-power pulses, beyond the 1 dB compression point of such amplifiers, we observe the appearance of echoes. These echoes have micro-second coherence, and we attribute their origin to microscopic defects in the amplifier dielectric layer. Furthermore, the application of such strong pulses bring the JTWPA in a highly nonlinear regime where its noise figure is compromised for several microseconds.

We realize an in-situ cancellation of these pulses that allows to mitigate both the effect of strong pulses on the device as well as dielectric echoes, recovering the typical gain and noise figure in 300 ns. These results can help in extending the use of JTWPAs in experiments where fast high-power sequences are necessary to generate weak microwave responses from the system under study.

We acknowledge IARPA and Lincoln Labs for providing a Josephson Traveling-Wave Parametric Amplifier.

[1] Macklin C et. al; Science. 2015 Oct 16; 350 (6258)