Control of Localized Multiple Excitation Dark States in Waveguide QED

TL;DR

This paper demonstrates the creation and control of localized multi-excitation dark states in waveguide QED systems, enabling high-fidelity photon storage and manipulation with minimal losses.

Contribution

It introduces a class of quasi-localized dark states at specific lattice constants, facilitating easier experimental preparation and readout compared to traditional fermionic states.

Findings

High-fidelity preparation of dark states in waveguide QED

Minimal loss and fast manipulation possible

Experimental implementation with superconducting qubits

Abstract

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.