Controlling Entanglement by Phase Engineering in Giant‐Atom Waveguide QED

ABSTRACT

We investigate the entanglement dynamics of two giant atoms coupled to a common waveguide. By introducing independently tunable coupling phases at each interaction point, each photon‐exchange path is jointly controlled by the phases at its two endpoints, enabling programmable manipulation of the atomic dynamics. Appropriate phase choices induce destructive interference and suppress selected photon‐exchange paths, reducing the nested configuration to an effective small‐atom model and establishing dynamical equivalence between separate and braided configurations. The suppression of selected photon‐exchange paths also reduces delayed information‐backflow effects, thereby reducing transient oscillations and accelerating the formation of steady‐state entanglement at finite time delays. In addition, the scheme markedly enhances the robustness of the entanglement dynamics against variations in the phase shift. These results provide a flexible framework for engineering photon‐exchange paths, entanglement storage, and memory effects in giant‐atom waveguide QED.