In my talk I will discuss different realizations of semi-conductor cavity-QED systems in which correlation effects play a defining role. In all cases, the enhanced light-matter interaction - one of the hallmarks of optoelectronic nanostructures - is the driving force that fosters correlations.
Coupling on-chip microwave cavities to superconducting microcircuits has provided a new platform to study the light/matter interaction at the most elementary level. Generalizing such a coupling to more complex quantum circuits, like quantum dot circuits, is of high interest since it would allow the use of different degrees of freedom, like for instance the electronic spin, in a cavity quantum electrodynamics context. In this talk, I will present various aspects of the effect of a double quantum dot on cavity photons. I will discuss the case of normal, ferromagnetic and superconducting reservoirs. In particular, the coupling of a Cooper pair splitter with cavity photons will be discussed
Recent progress in Cavity QED (CQED) has brought forth the possibility of wiring up individual CQED systems into lattices to investigate collective behavior and correlated phases of strongly coupled light and matter [1-9]. Such Lattice CQED systems operate on polaritonic quasi-particles that are hybrids of light and matter in a controllable proportion, combining long-range coherence of photons and strong interactions typically displayed by massive particles. In this talk, I will review recent work on proposed quantum simulation of Hubbard models with Lattice CQED systems, which are akin to the celebrated Bose-Hubbard model extensively studied with cold atomic gases in optical lattices and Josephson junction arrays. A crucial feature of Lattice CQED systems that I will focus on is their non-equilibrium nature. Unavoidable photon loss coupled with the ease of feeding in additional photons through continuous external driving renders such lattices open quantum systems. Under the influence of drive and dissipation, Lattice CQED systems typically display steady-state phases thereby providing a platform for realizing novel, non-equilibrium phases of light and matter that may be very dierent from those realized with condensed matter systems.
The structure of solids and their phases is mainly determined by static Coulomb forces while the coupling of charges to the dynamical, i.e., quantized degrees of freedom of the electromagnetic field plays only a secondary role. Recently, it has been speculated that this general rule can be overcome in the context of cavity quantum electrodynamics (QED), where the coupling of dipoles to a single field mode can be dramatically enhanced. Here we present a first exact analysis of the ground states of a dipolar cavity QED system in the non-perturbative coupling regime, where electrostatic and dynamical interactions play an equally important role. Specifically, we show how strong and long-range vacuum fluctuations modify the states of dipolar matter and induce novel phases with unusual properties. Beyond a purely fundamental interest, these general mechanisms can be important for potential applications, ranging from cavity-assisted chemistry to quantum technologies based on ultrastrongly coupled circuit QED systems.