Geometric control of maximal entanglement via bound states in the continuum

TL;DR

This paper demonstrates how geometric design in giant-atom waveguide systems can control maximal entanglement through bound states in the continuum, linking symmetry, geometry, and quantum entanglement.

Contribution

It introduces a method to achieve and control maximal entanglement via BICs in giant atoms, emphasizing the role of geometric parameters in entanglement tuning.

Findings

Maximally entangled states coincide with bound states in the continuum.

Entanglement is primarily determined by geometric design parameters.

Maximally entangled BICs exhibit robustness against parameter perturbations.

Abstract

Bound states in the continuum (BiCs) convert dissipative open systems into effectively closed quantum subspaces through destructive interference. We show that two identical giant atoms coupled to a one-dimensional waveguide support BICs that coincide with maximally entangled atomic states. Most importantly, entanglement is predominantly determined by the geometric design; the ratio of intra-atomic connection lengths fixes the concurrence, while the propagation phase between atoms selects a family of Bell-like states. We further analyze the dynamical stability of these maximally entangled BICs under exact time evolution, revealing a clear hierarchy of robustness against parameter perturbations. Our results establish an analytical bridge between symmetry, geometry, entanglement, and BICs in giant-atom waveguide platforms.