The ability to control the interaction between light and matter is the essence of many research disciplines including quantum information science, energy harvesting, and sensing. Enhancing the spontaneous emission rate of single quantum emitters is crucial in the realization of efficient single-photon sources, necessary for the development of quantum information technology and quantum cryptography. The control over the emission dynamics of semiconductor quantum dots is typically achieved by placing the quantum emitters within highly confining optical cavities  and waveguides . However, an alternative approach to achieve an efficient confinement of waves exists : disordered systems can be exploited to spatially localize light. We have demonstrated experimentally that these so-called Anderson-localized modes can form spontaneously in disordered photonic crystal waveguides and can be employed to dramatically enhance the light-matter interaction . By means of time-resolved photoluminescence spectroscopy, we measure enhancements of the spontaneous emission rate of single quantum dots up to a factor 15, with 94% of the emitted single-photons coupled to a single Anderson-localized mode. These results show that the performances of Anderson-localized cavities are comparable to state-of-the-art nano-cavities, proving the potentiality of disorder in light confinement. Disordered photonic media thus provide an efficient platform for quantum electrodynamics, offering a novel route to quantum information devices exploiting disorder as a resource rather than a nuisance.
 K.J. Vahala, “Optical microcavities”, Nature 424, 839 (2003).
 H. Thyrrestrup, L. Sapienza, P. Lodahl, “Extraction of the β-factor for single quantum dots coupled to a photonic crystal waveguide”, Appl. Phys. Lett. 96, 231106 (2010).
 L. Sapienza, H. Thyrrestrup, S. Stobbe, P.D. Garcia, S. Smolka, P. Lodahl, “Cavity quantum electrodynamics with Anderson-localized modes”, Science 327, 1352 (2010).