Abstract The entanglement transfer is investigated between giant atoms in waveguide‐QED systems. The two giant atom pairs, and , are independently coupled to their respective waveguides. Initially, entanglement are stored in atom pair . There three giant atom configurations are considered: separated, braided, and nested. For comparison, the small atom configuration is also studied here. The focus is on entanglement transfer from atom pair to atom pair and atom pair in these four coupling configurations. It is shown that the transfer of entanglement in each configuration strongly depends on phase shift. In particular, the braided configuration demonstrates superior performance in entanglement transfer. For the entanglement transfer from atom pair to atom pair , complete entanglement transfer is presented in braided configuration, a behavior not found in small atom or other giant atom configurations. For the entanglement transfer from atom pair to atom pair , although the maximum entanglement transferred to atom pair in the braided configuration is half of that one to atom pair , it is still higher than that in the small atom, separated, and nested configurations. This study lays the foundation for entanglement transfer between giant atoms in waveguide‐QED platforms.
Abstract The entanglement transfer is investigated between giant atoms in waveguide‐QED systems. The two giant atom pairs, and , are independently coupled to their respective waveguides. Initially, entanglement are stored in atom pair . There three giant atom configurations are considered: separated, braided, and nested. For comparison, the small atom configuration is also studied here. The focus is on entanglement transfer from atom pair to atom pair and atom pair in these four coupling configurations. It is shown that the transfer of entanglement in each configuration strongly depends on phase shift. In particular, the braided configuration demonstrates superior performance in entanglement transfer. For the entanglement transfer from atom pair to atom pair , complete entanglement transfer is presented in braided configuration, a behavior not found in small atom or other giant atom configurations. For the entanglement transfer from atom pair to atom pair , although the maximum entanglement transferred to atom pair in the braided configuration is half of that one to atom pair , it is still higher than that in the small atom, separated, and nested configurations. This study lays the foundation for entanglement transfer between giant atoms in waveguide‐QED platforms.
We study the generation of quantum entanglement between two giant atoms coupled to a one-dimensional waveguide. Since each giant atom interacts with the waveguide at two separate coupling points, there exist three different coupling configurations in the two-atom waveguide system: separated, braided, and nested couplings. Within the Wigner-Weisskopf framework for single coupling points, the quantum master equations governing the evolution of the two giant atoms are obtained. For each coupling configuration, the entanglement dynamics of the two giant atoms is studied, including the cases of two different atomic initial states: single- and double-excitation states. It is shown that the generated entanglement depends on the coupling configuration, phase shift, and atomic initial state. For the single-excitation initial state, there exists steady-state entanglement for these three couplings due to the appearance of the dark state. For the double-excitation initial state, an entanglement sudden birth is observed via adjusting the phase shift. In particular, the maximal entanglement for the nested coupling is about one order of magnitude larger than those of separate and braided couplings. In addition, the influence of the atomic frequency detuning on the entanglement generation is studied. This work can be utilized for the generation and control of atomic entanglement in quantum networks based on giant-atom waveguide-QED systems, which have wide potential applications in quantum information processing.
We study the generation of quantum entanglement between two giant atoms coupled to a common one-dimensional waveguide. Here each giant atom interacts with the waveguide at two separate coupling points. Within the Wigner-Weisskopf framework for single coupling points, we obtain the time-delayed quantum master equations governing the evolution of the two giant atoms for three different coupling configurations: separated, braided, and nested couplings. For each coupling configuration, we consider both the Markovian and non-Markovian entanglement dynamics of the giant atoms, which are initially in two different separable states: single- and double-excitation states. Our results show that the generated entanglement depends on the phase shift, time delay, atomic initial state, and the coupling configuration. For the single-excitation initial state, there exists the steady-state entanglement for each coupling in both the Markovian and non-Markovian regimes due to the appearance of the dark state. For the double-excitation initial state, we observe entanglement sudden birth via adjusting the phase shift in both regimes. In particular, the maximally achievable entanglement for the nested coupling is about one order of magnitude larger than those of separate and braided couplings. We also find that the maximal entanglement for these three coupling configurations can be enhanced in the case of small time delays. This work can be utilized for the generation and control of entanglement in quantum networks based on giant-atom waveguide-QED systems, which have wide potential applications in quantum information processing.
Abstract We study the entanglement generation of two giant atoms within a one-dimensional bidirectional-chiral waveguide quantum electrodynamics (QED) system, where the initial state of the two giant atoms are ∣ e a , g b 〉. Here, each giant atom is coupled to the waveguide through three connection points, with the configurations divided into five types based on the arrangement of coupling points between the giant atoms and the waveguide: separate, fully braided, partially braided, fully nested, and partially nested. We explore the entanglement generation process within each configuration in both nonchiral and chiral coupling cases. It is demonstrated that entanglement can be controlled as needed by either adjusting the phase shift or selecting different configurations. For nonchiral coupling, the entanglement of each configuration exhibits steady state properties attributable to the presence of dark state. In addition, we find that steady-state entanglement can be obtained at more phase shifts in certain configurations by increasing the number of coupling points between the giant atoms and the bidirectional waveguide. In the case of chiral coupling, the entanglement is maximally enhanced compared to the one of nonchiral case. Especially in fully braided configuration, the concurrence reaches its peak value 1, which is robust to chirality. We further show the influence of atomic initial states on the evolution of interatomic entanglement. Our scheme can be used for entanglement generation in chiral quantum networks of giant-atom waveguide-QED systems, with potential applications in quantum networks and quantum communications.
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.
We study the disentanglement dynamics of two giant atoms coupled to a common one-dimensional waveguide. We focus on the non-Markovian retarded effect in the disentanglement of the two giant atoms by taking the photon transmission time into account. By solving the time-delayed equations of motion for the probability amplitudes, we obtain the evolution of the entanglement of the two giant atoms, which are initially in the maximally entangled states in the single-excitation space. It is found that the retardation-induced non-Markovianity leads to nonexponential decay and revivals of entanglement. Concretely, we consider separate-, braided-, and nested-coupling configurations, and find that the disentanglement dynamics in these configurations exhibits different features. We demonstrate that the steady-state entanglement depends on the time delay under certain conditions in these three coupling configurations. We also study the dependence of the disentanglement of the two giant atoms on both the detuning effect and the initial-state phase effect. In addition, we consider the disentanglement dynamics of the two giant atoms, which are initially in the state superposed by zero-excitation and two-excitation components. This work will pave the way for the generation of stationary entanglement between two giant atoms, which may have potential applications in the construction of large-scale quantum networks based on the giant-atom waveguide-QED systems.
We investigate the entanglement dynamics of two giant atoms coupled to a common waveguide. By introducing additional phase modulation at each coupling point, every photon propagation path is jointly controlled by two distinct coupling phases, enabling precise and flexible manipulation of the entanglement evolution. This phase engineering induces destructive interference among different paths, leading to entanglement dynamics in nested giant atoms that become equivalent to those of small atoms, as well as dynamical equivalence between separated and braided configurations. Furthermore, the proposed scheme significantly enhances the robustness of entanglement against variations in the phase shift, offering a practical route to generate stable entanglement and enabling quantum devices with programmable propagation and controllable memory effects.