Fabrication of Josephson parameter amplifier and its application in squeezing vacuum fluctuations*

Abstract

Josephson parameter amplifier (JPA) is a microwave signal amplifier device with near-quantum-limit-noise performance. It has important applications in scientific research fields such as quantum computing and dark matter detection. This work reports the fabrication and characterization of broadband JPA devices and their applications in multi-qubit readout and squeezing of vacuum state. We use a process in which transmission lines and electrodes are made of niobium thin film and aluminum Josephson junctions are made by Dolan bridge technique. We believe this process is more convenient than the process we used previously. The whole production process adopts electron beam lithography technology to ensure high structural resolution. The test result shows that the gain value of the manufactured JPA can exceed 15 dB, and the amplification bandwidth is about 400 MHz. The noise temperature is about 400 mK at the working frequency of 6.2 GHz. The devices have been successfully used in experiments involving superconducting multi-qubit quantum processors. Furthermore, the device is applied to squeeze vacuum fluctuations and a squeezing level of 1.635 dB is achieved.