Mitigating quantum decoherence and enhancing long-range entanglement are critical to the advancement of quantum information applications. We propose a photonic crystal-air-photonic crystal sandwich-structured waveguide system, which exhibits zero index by utilizing the accidental degeneracy between the waveguide mode and two bound modes. We evaluate transient and steady-state quantum information (including entanglement and coherence), demonstrating the robust generation of quantum resources over arbitrarily long distances. To the best of our knowledge, this work represents the first realization of an ideal long-range quantum-resource generator based on a zero-index waveguide.
Qin et al. (Mon,) studied this question.