Cavity Quantum Electrodynamics with Anderson-Localized Modes

Scattered and Coupled Cavity electrodynamics explores the coupling of light with matter—ideally, that of a single photon with a single atom. Typically, this requires that the photon and the atom be confined to increase the likelihood of interaction, but scattering of light is an unavoidable product of an engineered device and is usually considered to be detrimental because it leads to loss of the photons from the cavity. Sapienza et al. (p. 1352; see the Perspective by Wiersma) saw extreme light scattering as an opportunity for the spontaneous generation of localized modes of light that can be exploited to induce light-matter coupling. Thus, working with a process where scattering is considered a resource rather than a nuisance, as in this case, may prove useful for realizing robust quantum information devices. Optical scattering is used to induce quantum coupling between light and an artificial atom. A major challenge in quantum optics and quantum information technology is to enhance the interaction between single photons and single quantum emitters. This requires highly engineered optical cavities that are inherently sensitive to fabrication imperfections. We have demonstrated a fundamentally different approach in which disorder is used as a resource rather than a nuisance. We generated strongly confined Anderson-localized cavity modes by deliberately adding disorder to photonic crystal waveguides. The emission rate of a semiconductor quantum dot embedded in the waveguide was enhanced by a factor of 15 on resonance with the Anderson-localized mode, and 94% of the emitted single photons coupled to the mode. Disordered photonic media thus provide an efficient platform for quantum electrodynamics, offering an approach to inherently disorder-robust quantum information devices.