Tunable Anderson Localization of Dark States

TL;DR

This paper demonstrates tunable Anderson localization of dark states in a superconducting waveguide system with controllable qubit disorder, revealing exponential transmission suppression and localization length dependence on disorder strength.

Contribution

It introduces a novel platform for studying photon localization with in-situ tunable disorder and coupling via a common waveguide, advancing understanding of open-system localization phenomena.

Findings

Transmission suppression near dark modes increases with disorder

Localization length decreases as disorder strength increases

Supports experimental results with a one-dimensional non-interacting model

Abstract

Random scattering of photons in disordered one-dimensional solids gives rise to an exponential suppression of transmission, which is known as Anderson localization. Here, we experimentally study Anderson localization in a superconducting waveguide quantum electrodynamics system comprising eight individually tunable qubits coupled to a photonic continuum of a waveguide. Employing the qubit frequency control, we artificially introduce frequency disorder to the system and observe an exponential suppression of the transmission coefficient in the vicinity of its subradiant dark modes. The localization length decreases with the disorder strength, which we control in-situ by varying individual qubit frequencies. Employing a one-dimensional non-interacting model of coupled qubits and photons, we are able to support and complement the experimental results. The difference between our investigation and previous studies of localization in qubit arrays is the coupling via a common waveguide, allowing us to explore the localization of mediating photons in an intrinsically open system. The experiment opens the door to the study of various localization phenomena on a new platform, which offers a high degree of control and readout possibilities.