Giant-atom entanglement in waveguide-QED systems including non-Markovian effect

TL;DR

This paper investigates how giant atoms coupled to a waveguide can generate and control quantum entanglement, considering non-Markovian effects and different coupling configurations, with implications for quantum networks.

Contribution

It introduces a comprehensive analysis of entanglement dynamics in giant-atom waveguide-QED systems including non-Markovian effects and various coupling geometries, revealing conditions for steady-state and enhanced entanglement.

Findings

Steady-state entanglement exists for single-excitation states in all configurations.

Entanglement sudden birth can be achieved by phase shift adjustment.

Nested coupling yields the highest maximal entanglement among configurations.

Abstract

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.