Photonic Reservoir Engineering via 2D $\Lambda$-Type Atomic Arrays in Waveguide QED

TL;DR

This paper introduces 2D atomic lattice geometries coupled to waveguides to improve quantum memory and nonlinear optics by engineering collective atomic modes, surpassing limitations of 1D systems.

Contribution

Proposes Zigzag and Orthogonal 2D atomic lattice geometries that enhance EIT bandwidth and nonlinear photon generation compared to traditional 1D setups.

Findings

Broadened EIT window with suppressed scattering in Zigzag lattice.

Six orders of magnitude increase in four-wave mixing efficiency.

Localized spectral modes for idler photons.

Abstract

Electromagnetically induced transparency (EIT) in $\Lambda$-type atomic systems underpins quantum technologies such as high-fidelity memory and nonlinear optics, but conventional setups face intrinsic limitations. Standard geometries of one-dimensional atomic chains coupled to waveguides allow only a single bright superradiant channel, while subradiant modes remain weakly accessible, limiting control over collective radiative behavior and dark-state pathways. This leads to unwanted inelastic processes, degrading memory fidelity and reducing nonlinear photon generation efficiency. Here, we propose two two-dimensional (2D) atomic lattice geometries coupled to a photonic crystal waveguide, namely Zigzag and Orthogonal structures. In the Zigzag model, engineered collective super- and subradiant modes produce a flattened EIT window, broadening the transmission bandwidth and suppressing unwanted scattering to enhance quantum memory fidelity. In the Orthogonal model, four-wave mixing (FWM) intensity is amplified by up to six orders of magnitude relative to a conventional one-dimensional $\Lambda$-type EIT chain with identical $\Gamma_{1D}$, $\Omega_c$, and probe intensity, with localized idler photons forming well-defined spectral modes. These results demonstrate a versatile route to engineer structured photonic reservoirs for on-demand photon generation, high-fidelity quantum storage, and enhanced nonlinear optical processes.