Quantum Amplifiers With Very High Bandwidths

IQ’s call for projects is an opportunity for collaboration and experience sharing that offers a great deal of independence to researchers. Sébastien Jézouin and Udson Mendes, IQ postdoctoral fellows, have seized this opportunity and submitted a project to build a quantum amplifier.

To survive ambient temperatures and contribute to the effective transmission of quantum information, an amplifier is required to boost a signal as weak as a single photon. At present, many amplifiers already work well but their bandwidths are narrow and they amplify signals on low frequency ranges, which is not optimal. There are only a handful of examples of effective amplifiers with a large bandwidth. However, these are difficult to build because of the complexity of the technical feat required to produce them.

The two researchers have combined their expertise to design a quantum-limited amplifier, equipped with a bandwidth of several GHz, with a relatively simple architecture. They have dedicated the first portion of the project to develop design scenarios and find solutions to experimental problems caused by theoretical constraints. Sébastien Jézouin, the experimenter, and Udson Cabral, the theorist, have taken advantage of the opportunity to spend time together daily to drive the project forward.

The result: with a bandwidth of 3-dB reaching 4.3 GHz, they demonstrated a gain of 20 dB, corresponding to the kind of performances expected at the start. All this was the subject of an article in Physical Review Applied.

This project has also enabled the two researchers to explore intellectual property, supported in their efforts by IQ.

arametric amplification and squeezing with an ac- and dc-voltage biased superconducting junction