Dynamical excitation control and multimode emission of an atom-photon bound state

Atom-photon bound states (APBS) arise through the coupling of quantum emitters to the band-edge of a dispersion-engineered waveguide. These bound states can mediate long-range interactions and are promising candidates for quantum simulation.

Complementing recent studies on interacting APBSs, we study the dynamics of an APBS, with superconducting quantum circuits, using a frequency tunable transmon and a photonic crystal waveguide. This waveguide is fabricated using 21 nearest-neighbor coupled, compact, high-impedance superconducting microwave resonators. Employing precise temporal control over the qubit frequency detuning from the band-edge, we examine the transition from adiabatic to non-adiabatic behavior in the formation and collapse of the bound state. We experimentally observe multimode emission from our photonic crystal, triggered by bound state excitation quenching in the non-adiabatic regime. Our characterization of the formation and collapse of APBS and their dynamical release into propagating modes in waveguides facilitates their use in quantum simulation, quantum optics, and communication.