Using multipartite entanglement measure, we investigate the entanglement generation among three atoms coupling to a semiinfinite waveguide. The effects of the separation distance between the atoms, the chiral coupling strength, and the distance between the finite end of the waveguide and the atoms are considered. Due to the mirror-induced quantum coherent feedback, the equations for the atoms’ state are time-delay differential equations. By simulation, we find that the entanglement among the three atoms is long-lasting, and its evolution depends on the separation distance between atoms, the chiral coupling strength, and the distance between the finite end of the mirror and the atoms. With a negligible time delay, the chiral coupling affects the entanglement evolution. The stronger the chiral coupling is, the faster the entanglement culminates and then decreases to zero. Our results indicate that the three-atom entanglement can be generated by controlling the separation distance between the atoms, the chiral coupling strength, and the distance between the finite end of the waveguide and the atoms. Our study contributes to understanding the multipartite entanglement generation based on waveguide-atom systems.
Using multipartite entanglement measure, we investigate the entanglement generation among three atoms coupling to a semiinfinite waveguide. The effects of the separation distance between the atoms, the chiral coupling strength, and the distance between the finite end of the waveguide and the atoms are considered. Due to the mirror-induced quantum coherent feedback, the equations for the atoms’ state are time-delay differential equations. By simulation, we find that the entanglement among the three atoms is long-lasting, and its evolution depends on the separation distance between atoms, the chiral coupling strength, and the distance between the finite end of the mirror and the atoms. With a negligible time delay, the chiral coupling affects the entanglement evolution. The stronger the chiral coupling is, the faster the entanglement culminates and then decreases to zero. Our results indicate that the three-atom entanglement can be generated by controlling the separation distance between the atoms, the chiral coupling strength, and the distance between the finite end of the waveguide and the atoms. Our study contributes to understanding the multipartite entanglement generation based on waveguide-atom systems.
We investigate the entanglement dynamics of two two-level emitters (qubits) mediated by a semi-infinite, one-dimensional photonic waveguide. The coupling of each qubit to the waveguide is chiral, which depends on the propagation direction of light. The finite end of the waveguide is terminated by a perfect mirror such that coherent quantum feedback is introduced to the system. We show that the chirally generated entanglement between the qubits can be preserved by controlling the time delay of the feedback. Moreover, when the time delay is negligible, the qubit-qubit reduced system evolves within the strong-coupling regime and the qubits can be almost maximally entangled. We also analyze the robustness of the protocol against variations of some relevant parameters.
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.
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.
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 explore the generation and optimization of entanglement between atoms chirally coupled to finite one-dimensional spin chains, functioning as spin cavities. By diagonalizing the spin cavity Hamiltonian, we identify a parity effect that influences entanglement, with small even-sized cavities chirally coupled to atoms expediting entanglement generation by approximately 50 % faster than nonchiral coupling. Applying a classical driving field to the atoms reveals oscillations in concurrence, with resonant dips at specific driving strengths due to the resonances between the driven atom and the spin cavity. Extending our study to systems with energetic disorder, we find that high concurrence can be achieved regardless of disorder strength when the inverse participation ratio of the resulting eigenstates is favorable. Finally, we demonstrate that controlled disorder within the cavity significantly enhances and expedites entanglement generation, achieving higher concurrences up to four times faster than those attained in ordered systems.
We study the dissipative dynamics of an atom in a V-level configuration driven by lasers and coupled to a semi-infinite waveguide. The coupling to the waveguide is chiral, in that each transition interacts only with the modes propagating in a given direction, and this direction is opposite for the two transitions. The waveguide is terminated by a mirror which coherently feeds the photon stream emitted by one transition back to the atom. First, we are interested in the dynamics of the atom in the Markovian limit where the time delay in the feedback is negligible. Specifically, we study the conditions under which the atom evolves towards a pure ``dark'' stationary state, where the photons emitted by both transitions interfere destructively thanks to the coherent feedback, and the overall emission vanishes. This is a single-atom analog of the quantum dimer, where a pair of laser-driven two-level atoms is coupled to a unidirectional waveguide and dissipates towards a pure entangled dark state. Our setup should be feasible with current state-of-the-art experiments. Second, we extend our study to non-Markovian regimes and investigate the effect of the feedback retardation on the steady state.