Decoherence-free interaction and maximally entangled state generation in giant-atom semi-infinite waveguide systems

TL;DR

This paper demonstrates that decoherence-free interactions and maximally entangled states can be achieved with giant atoms in semi-infinite waveguides, revealing new configurations for robust quantum entanglement.

Contribution

It introduces novel configurations for giant atoms in semi-infinite waveguides to realize decoherence-free interactions and generate maximally entangled states, expanding the understanding of waveguide-QED systems.

Findings

Decoherence-free interaction occurs in braided and nested configurations in semi-infinite waveguides.

Maximally entangled states are generated due to DFI in these configurations.

Entanglement can exceed 0.5 in the separate configuration.

Abstract

Giant atoms are artificial atoms that can couple to a waveguide non-locally. Previous works have shown that two giant atoms in a braided configuration can interact through one-dimensional (1D) infinite and chiral waveguides, with both individual and collective atomic relaxation being fully suppressed. In this paper, however, we show that the decoherence-free interaction (DFI) between two giant atoms can be realized in both braided and nested configurations when the waveguide is semi-infinite. This protected interaction fails to appear in semi-infinite waveguide systems containing two separate giant atoms or two small atoms. We also study the entanglement generation between two giant atoms coupled to a 1D semi-infinite waveguide. The results show that the maximally entangled state is generated in both braided and nested configurations due to the formation of DFI, and in the separate configuration, the maximally achievable entanglement can exceed 0.5. Finally, we generalize the discussion on DFI and entanglement generation to the case involving multiple giant atoms coupled into a semi-infinite waveguide. This study presents a new scheme for realizing DFI and generating maximally entangled states in giant-atom waveguide-QED systems.