Designing frequency-dependent relaxation rates and Lamb shift for a giant artificial atom

TL;DR

This paper explores how multiple coupling points in a giant artificial atom lead to frequency-dependent relaxation rates and Lamb shifts, enabling tailored quantum interactions for advanced quantum technologies.

Contribution

It introduces a theoretical framework for designing frequency-dependent relaxation and Lamb shift in giant artificial atoms with multiple coupling points.

Findings

Frequency dependence is given by the discrete Fourier transform of coupling points.

Designable coupling strength and Lamb shift based on coupling point arrangement.

Potential applications include tunable coupling and single-atom lasing.

Abstract

In traditional quantum optics, where the interaction between atoms and light at optical frequencies is studied, the atoms can be approximated as point-like when compared to the wavelength of light. So far, this relation has also been true for artificial atoms made out of superconducting circuits or quantum dots, interacting with microwave radiation. However, recent and ongoing experiments using surface acoustic waves show that a single artificial atom can be coupled to a bosonic field at several points wavelengths apart. Here, we theoretically study this type of system. We find that the multiple coupling points give rise to a frequency dependence in the coupling strength between the atom and its environment, and also in the Lamb shift of the atom. The frequency dependence is given by the discrete Fourier transform of the coupling point coordinates and can therefore be designed. We discuss a number of possible applications for this phenomenon, including tunable coupling, single-atom lasing, and other effects that can be achieved by designing the relative coupling strengths of different transitions in a multi-level atom.