Lamb shift of a lossy two-level emitter inside a leaky cavity: A universal description based on an equivalent dissipative model

Abstract

We present an universal description for Lamb shift of a lossy two-level-emitter (TLE) inside a leaky cavity by combining the quantum dissipation theory and the perturbative treatment developed in cavity QED. The total spectrum function of bath associated with the TLE is deduced by the standard method developed for a quantum dissipation model, from which the total spontaneous emission rate and Lamb shift are calculated. The developed calculation scheme is able to reproduce the known Purcell enhancement factor and is shown to be in agreement with the analysis made for a confocal resonator. It is found that the Lamb shift due to a leaky cavity mode has a sharp drop when sweeping across the resonance point. The physics behind this unusual behavior and the related experimental observations made on both atom-cavity and quantum-dot cavity systems are also analyzed.