Subradiant excited states in finite chains of two-level quantum emitters coupled to a one-dimensional reservoir are a resource for superior photon storage and controlled photon manipulation. Typically, states storing multiple excitations exhibit fermionic correlations and are thus characterized by an anti-symmetric wavefunction, which makes them hard to prepare experimentally. Here we identify a class of quasi-localized dark states with up to half of the qubits excited, which appear for lattice constants that are an integer multiple of the guided-mode wavelength. They allow for a high-fidelity preparation and minimally invasive read out in state-of-the-art setups. In particular, we suggest an experimental implementation using a coplanar wave-guide coupled to superconducting transmon qubits on a chip. As free space and intrinsic losses are minimal, virtually perfect dark states can be achieved even for a low number of qubits, enabling fast preparation and manipulation with high fidelity.
@article{arxiv.2209.09212,
title = {Control of Localized Multiple Excitation Dark States in Waveguide QED},
author = {Raphael Holzinger and Ricardo Gutierrez-Jauregui and Teresa Hönigl-Decrinis and Gerhard Kirchmair and Ana Asenjo-Garcia and Helmut Ritsch},
journal= {arXiv preprint arXiv:2209.09212},
year = {2022}
}