Exciting Dressed BICs Via Photon Scattering and Delayed Quantum Feedback

We consider a semi-infinite waveguide with linear dispersion coupled to a qubit, in which a dressed bound state in the continuum (BIC) is known to exist. We predict that this BIC can be excited with significant probability via multi-photon scattering in the non-Markovian regime where the photon delay time (corresponding to the qubit-mirror distance) is of the order of the qubit’s decay time. A similar process excites the BIC existing in an infinite waveguide coupled to a pair of qubits, yielding stationary entanglement between them. This shows, in particular, that photon trapping via scattering can occur without band-edge effects or cavities, the essential resource being instead the delayed quantum feedback due to the mirror.

Manipulation of the stationary entanglement of three atoms coupled to a common environment

In this work, we study the dynamics of three entangled atoms coupled to a common structured reservoir. The atoms are initially prepared in different W-like states characterized by different relative phases. We examine the roles of initial relative phases on the energy transfers among the individual atoms as well as atomic entanglement dynamics. We show that the features of quantum interferences induced by initial relative phases greatly affect the energy transfers and entanglement dynamics. In particular, a suitable choice of initial phases can increase atomic stationary entanglement over their initial value. The results imply a possible control strategy for atomic entanglement dynamics.