Dephasing of Mollow Triplet Sideband Emission of a Resonantly Driven Quantum Dot in a Microcavity

Detailed properties of resonance fluorescence from a single quantum dot in a micropillar cavity are investigated, with particular focus on emission coherence in dependence on optical driving field power and detuning. Power-dependent series over a wide range could trace characteristic Mollow triplet spectra with large Rabi splittings of $|\Omega| \leq 15$ GHz. In particular, the effect of dephasing in terms of systematic spectral broadening $\propto \Omega^2$ of the Mollow sidebands is observed as a strong fingerprint of excitation-induced dephasing. Our results are in excellent agreement with predictions of a recently presented model on phonon-dressed QD Mollow triplet emission in the cavity-QED regime

Indistinguishable photons from the resonance fluorescence of a single quantum dot in a microcavity

We demonstrate purely resonant continuous-wave optical laser excitation to coherently prepare an excitonic state of a single semiconductor quantum dot (QDs) inside a high quality pillar microcavity. As a direct proof of QD resonance fluorescence, the evolution from a single emission line to the characteristic Mollow triplet10 is observed under increasing pump power. By controlled utilization of weak coupling between the emitter and the fundamental cavity mode through Purcell-enhancement of the radiative decay, a strong suppression of pure dephasing is achieved, which reflects in close to Fourier transform-limited and highly indistinguishable photons with a visibility contrast of 90%. Our experiments reveal the model-like character of the coupled QD-microcavity system as a promising source for the generation of ideal photons at the quantum limit. From a technological perspective, the vertical cavity symmetry -- with optional dynamic tunability -- provides strongly directed light emission which appears very desirable for future integrated emitter devices.Comment: 24 pages, 6 figure

The Geometry and Ionization Structure of the Wind in the Eclipsing Nova-like Variables RW Tri and UX UMa

The UV spectra of nova-like variables are dominated by emission from the accretion disk, modified by scattering in a wind emanating from the disk. Here we model the spectra of RW Tri and UX UMa, the only two eclipsing nova-likes which have been observed with the Hubble Space Telescope in the far-ultraviolet, in an attempt to constrain the geometry and the ionization structure of their winds. Using our Monte Carlo radiative transfer code we computed spectra for simply-parameterized axisymmetric biconical outflow models and were able to find plausible models for both systems. These reproduce the primary UV resonance lines - N V, Si IV, and C IV - in the observed spectra in and out of eclipse. The distribution of these ions in the wind models is similar in both cases as is the extent of the primary scattering regions in which these lines are formed. The inferred mass loss rates are 6% to 8% of the mass accretion rates for the systems. We discuss the implication of our point models for our understanding of accretion disk winds in cataclysmic variables.Comment: 13 pages, 15 figures and 4 tables. Published in Ap

200 A GeV Au+Au collisions serve a nearly perfect quark-gluon liquid

The specific shear viscosity (eta/s)_QGP of a Quark-Gluon-Plasma (QGP) at temperatures T_c < T < 2T_c is extracted from the centrality dependence of the eccentricity-scaled elliptic flow measured in ultra-relativistic heavy-ion collisions. Coupling viscous fluid dynamics for the QGP with a microscopic transport model for hadronic freeze-out we find that the eccentricity-scaled elliptic flow is a universal function of charged multiplicity per unit overlap area, (1/S)(dN_ch/dy), that depends only on the viscosity but not on the model used for computing the initial fireball eccentricity. Comparing with measurements we find 1 < (4pi)(eta/s)_QGP < 2.5 where the uncertainty range is dominated by model uncertainties for the eccentricity values used to normalize the measured elliptic flow.Comment: 4 pages, 2 figures, accepted by PR

Event-by-event shape and flow fluctuations of relativistic heavy-ion collision fireballs

Heavy-ion collisions create deformed quark-gluon plasma (QGP) fireballs which explode anisotropically. The viscosity of the fireball matter determines its ability to convert the initial spatial deformation into momentum anisotropies that can be measured in the final hadron spectra. A quantitatively precise empirical extraction of the QGP viscosity thus requires a good understanding of the initial fireball deformation. This deformation fluctuates from event to event, and so does the finally observed momentum anisotropy. We present a harmonic decomposition of the initial fluctuations in shape and orientation of the fireball and perform event-by-event ideal fluid dynamical simulations to extract the resulting fluctuations in the magnitude and direction of the corresponding harmonic components of the final anisotropic flow at midrapidity. The final harmonic flow coefficients are found to depend non-linearly on the initial harmonic eccentricity coefficients. We show that, on average, initial density fluctuations suppress the buildup of elliptic flow relative to what one obtains from a smooth initial profile of the same eccentricity, and discuss implications for the phenomenological extraction of the QGP shear viscosity from experimental elliptic flow data.Comment: 22 pages, 17 figures. Relative to [v2], minor changes in text. Fig. 9 redrawn. This version accepted by Phys. Rev.