Observation of a broadband Lamb shift in an engineered quantum system

TL;DR

This paper reports the first observation of a broadband Lamb shift in superconducting resonators, demonstrating tunable energy shifts via engineered environments, which advances control in quantum systems and opens new research avenues.

Contribution

It presents the experimental observation of a broadband Lamb shift in superconducting resonators with tunable environment, a novel achievement in engineered quantum systems.

Findings

Measured a several megahertz shift in resonator frequency

Achieved tunable broadband Lamb shift via hybrid tunnel junctions

Demonstrated control of dissipation in quantum systems

Abstract

The shift of energy levels owing to broadband electromagnetic vacuum fluctuations, the Lamb shift, has been pivotal in the development of quantum electrodynamics and in understanding atomic spectra. Currently, small energy shifts in engineered quantum systems are of paramount importance owing to the extreme precision requirements in applications such as quantum computing. However, without a tunable environment it is challenging to resolve the Lamb shift in its original broadband case. Consequently, the observations in other than atomic systems are limited to environments comprised of narrow-band modes. Here, we observe a broadband Lamb shift in high-quality superconducting resonators, a scenario also accessing static shifts inaccessible in Lamb's experiment. We measure a continuous change of several megahertz in the fundamental resonator frequency by externally tuning the coupling strength of the engineered broadband environment which is based on hybrid normal-metal--superconductor tunnel junctions. Our results may lead to improved control of dissipation in high-quality engineered quantum systems and open new possibilities for studying synthetic open quantum matter using this hybrid experimental platform.