Vortices in exciton-polariton condensates with polarization splitting

The presence of polarization splitting of exciton-polariton branches in planar semiconductor microcavities has a pronounced effect on vortices in polariton condensates. We show that the TE-TM splitting leads to the coupling between the left and right half-vortices (vortices in the right and left circular components of the condensate), that otherwise do not interact. We analyze also the effect of linear polarization pinning resulted from a fixed splitting between two perpendicular linear polarizations. In this case, half-vortices acquire strings (solitons) attached to them. The half-vortices with strings can be detected by observing the interference fringes of light emitted from the cavity in two circular polarizations. The string affects the fringes in both polarizations. Namely, the half-vortex is characterized by an asymmetric fork-like dislocation in one circular polarization; the fringes in the other circular polarization are continuous, but they are shifted by crossing the string.Comment: 4 pages, 2 figs, Optics of Excitons in Confined Systems 11 (Madrid, 7-11 september 2009

Harvesting, coupling and control of single exciton coherences in photonic waveguide antennas

We perform coherent non-linear spectroscopy of individual excitons strongly confined in single InAs quantum dots (QDs). The retrieval of their intrinsically weak four-wave mixing (FWM) response is enabled by a one-dimensional dielectric waveguide antenna. Compared to a similar QD embedded in bulk media, the FWM detection sensitivity is enhanced by up to four orders of magnitude, over a broad operation bandwidth. Three-beam FWM is employed to investigate coherence and population dynamics within individual QD transitions. We retrieve their homogenous dephasing in a presence of spectral wandering. Two-dimensional FWM reveals off-resonant F\"orster coupling between a pair of distinct QDs embedded in the antenna. We also detect a higher order QD non-linearity (six-wave mixing) and use it to coherently control the FWM transient. Waveguide antennas enable to conceive multi-color coherent manipulation schemes of individual emitters.Comment: 7 pages, 8 Figure

Quantum correlations on quantum spaces

For given quantum (non-commutative) spaces $\mathbb{P}$ and $\mathbb{O}$, we study the quantum space of maps $\mathbb{M}_{\mathbb{P}, \mathbb{O}}$, from $\mathbb{P}$ to $\mathbb{O}$. In case of finite quantum spaces, these objects turn out to be behind a large class of maps which generalize the classical qc-correlations known from quantum information theory to the setting of quantum input and output sets. We prove various operator algebraic properties of the C* -algebras C($\mathbb{M}_{\mathbb{P}, \mathbb{O}}$) such as the lifting property and residual finite dimensionality. Inside C($\mathbb{M}_{\mathbb{P}, \mathbb{O}}$) we construct a universal operator system $\mathbb{S}_{\mathbb{P}, \mathbb{O}}$ related to $\mathbb{P}$ and $\mathbb{O}$, and show, among other things, that the embedding $\mathbb{S}_{\mathbb{P}, \mathbb{O}} \subset$ C($\mathbb{M}_{\mathbb{P}, \mathbb{O}}$) is hyperrigid and has another interesting property, which we call the strong extension property. Furthermore, C($\mathbb{M}_{\mathbb{P}, \mathbb{O}}$) is the C* -envelope of $\mathbb{S}_{\mathbb{P}, \mathbb{O}}$ and a large class of non-signalling correlations on the quantum sets $\mathbb{P}$ and $\mathbb{O}$ arise from states on C($\mathbb{M}_{\mathbb{P}, \mathbb{O}}$) ⊗$_{max}$ C($\mathbb{M}_{\mathbb{P}, \mathbb{O}}$) as well as states on the commuting tensor product $\mathbb{S}_{\mathbb{P}, \mathbb{O}}$ ⊗$_{c} \mathbb{S}_{\mathbb{P}, \mathbb{O}}$. Finally, we introduce and study the notion of a synchronous correlation with quantum input and output sets and prove several characterizations of such correlations and their relation to traces on C($\mathbb{M}_{\mathbb{P}, \mathbb{O}}$