Quantum interference and controllable magic cavity QED via a giant atom in a coupled resonator waveguide

We study the Markovian and non-Markovian dynamics in a giant atom system which couples to a coupled resonator waveguide (CRW) via two distant sites. Under certain conditions, we find that the giant atom population can exhibit an oscillating behavior and the photon can be trapped in the giant atom regime. These phenomena are induced by the interference effect among the bound states both in and outside the continuum, which is peculiar for two-site atom-CRW coupling. As an application of the photon trapping, we theoretically propose a magic cavity model where the giant atom serves as either a perfect or leaky cavity, depending on the distance between the coupling sites. The controllability of the magic cavity from a perfect to a leaky one cannot be realized in the traditional cavity or circuit QED setup. The predicted effects can be probed in state-of-the-art waveguide QED experiments and provide a striking example of how the different kinds of bound states modify the dynamics of a quantum open system in a structured environment.