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

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.

Perfect photon absorption based on the optical parametric process

The perfect photon absorption is studied in a cavity quantum electrodynamics(CQED) system, in which an optical parameter amplifier(OPA) is coupled to the cavity mode. This makes it possible to control the optical phase to realize the perfect photon absorption. It is found that in the presence of one and two injected fields, the perfect photon absorption is present in these two cases and can be controlled by adjusting the parametric phase. Moreover, different from the previous predictions of perfect photon absorption in atomic CQED systems, the perfect photon absorption can be changed significantly by the relative phase. Our work provides a new platform to use the parametric processes to make an available way to control the behaviors of photons and to take advantage of the optical phase to achieve the perfect photon absorption.

Fabrication and characterization of ultra-low noise narrow and wide band Josephson parametric amplifiers

We have fabricated two types of lumped-element Josephson parameter amplifiers（JPAs） by using a multilayer microfabrication process involving wet etching of Al films. The first type is a narrow band JPA which shows typical gain above14 dB in a bandwidth around 35 MHz. The second type is a wideband JPA which is coupled to an input 50Ω transmission line via an impedance transformer that changes the impedance from about 15 Ω on the non-linear resonator side to 50 Ωon the input transmission line side. The wideband JPA could operate in a 200 MHz range with a gain higher than 14 d B.The amplifiers were used for superconducting qubit readout. The results showed that the signal to noise ratio and hence the readout fidelity were improved significantly.

The Effect of System and Amplifier Parameters on the Performance of Average Soliton Transmission System Using PSA as In-Line Amplifier

In this paper,the effect of system and amplifier parameters on the performance of soliton transmission systemusing Phase Sensitive Amplifier(PSA)as in-line amplifier has been researched theoretically by computer simulation.Since in PSA soliton system the performance of average soliton regime is much better than that of dynamic soliton regime,in our simulation we only considered average soliton regime.Our simulation results show that although using PSA as in-line amplifiers in soliton system can not only overcome Gordon-Haus restriction but also suppress solitons interaction,lengthen soliton stable transmission distance significantly,the system and amplifier parameters have to be chosen carefullyin order to get a better system perorformance.

Gain Flattened Raman Fiber Amplifier Using Parameter Optimization and DCF Fiber

We investigate two configurations of Raman fiber amplifier in the 1530-1570 nm region. The gain spectrum variation is decreased from 8.31 dB to 2.48 dB when appropriately adjust the individual two pumps and optical fiber.