Ana Asenjo Garcia - California Institute of Technology
Dissipation is a pervasive problem in many areas of physics. In quantum optics, losses curb our ability to realize controlled and efficient interactions between photons and atoms, which are essential for many technologies ranging from quantum information processing to metrology. Spontaneous emission - in which photons are first absorbed by atoms and then re-scattered into undesired channels - imposes a fundamental limit in the fidelities of many quantum applications, such as quantum memories and gates. Typically, it is assumed that this process occurs at a rate given by a single isolated atom. However, this assumption can be dramatically violated: interference in photon emission and absorption generates correlations and entanglement among atoms, thus making dissipation a collective phenomenon. In this talk, I will provide a comprehensive look into the physics of subradiance, an emergent form of correlated dissipation in which interference is destructive and atomic decay is inhibited. In atomic arrays in free space, subradiant states acquire an elegant interpretation in terms of optical guided modes, which only emit due to scattering from the ends of the finite system. By interfacing atomic chains with nanophotonic structures, these states can be excited straightforwardly. Exploiting their radiative properties allows for the realization of a quantum memory with a photon retrieval fidelity that performs exponentially better with number of atoms than previously known bounds. This single example illustrates how correlated dissipation transcends the "standard model" of disordered atomic ensembles, and suggests that we should re-examine well-known concepts in quantum optics in a new light.