Remote Macroscopic Entanglement on a Photonic Crystal Architecture

The outstanding progress in nanostructure fabrication and cooling technologies allows what was unthinkable a few decades ago: bringing single-mode mechanical vibrations to the quantum regime. The coupling between photon and phonon excitations is a natural source of nonclassical states of light and mechanical vibrations, and its study within the field of cavity optomechanics is developing lightning-fast. Photonic crystal cavities are highly integrable architectures that have demonstrated the strongest optomechanical coupling to date, and should therefore play a central role for such hybrid quantum state engineering. In this context, we propose a realistic heralding protocol for the on-chip preparation of remotely entangled mechanical states, relying on the state-of-the-art optomechanical parameters of a silicon-based nanobeam structure. Pulsed sideband excitation of a Stokes process, combined with single photon detection, allows writing a delocalised mechanical Bell state in the system, signatures of which can then be read out in the optical field. A measure of entanglement in this protocol is provided by the visibility of a characteristic quantum interference pattern in the emitted light.Comment: 8 pages, 5 Figure

The threshold criteria for the 75g oral glucose tolerance test in pregnancy and short-term adverse pregnancy outcomes

The significant threshold values for the 75g oGTT during pregnancy have yet to be conclusively determined. The study aims to identify the risk significance of a borderline oGTT result. Women undergoing a 75g OGTT during the third trimester of pregnancy were classified into two groups - borderline tolerance (2-h post-load glucose 8.0-8.5 mmol/l: n=75), and GDM (2:8.6 mmol/l: n=236). Outcome indicators of these two groups of women were compared to the parameters of the women with a presumed normal carbohydrate metabolism (n = 12185). GDM women showed themselves to be at a significantly increased risk of developing hypertensive disorders during pregnancy and to require obstetric intervention in the form of induction of labour and caesarean section. Their infants were more likely to be macrosomic or preterm and having a low Apgar score at birth. Shoulder dystocia was similarly more likely in infants born to GDM mothers. Women with borderline glucose tolerance did not in any way show any statistically significant increased predisposition to these complications. It would appear the significant threshold for the 75g oGTT during pregnancy should be of the order proposed by the American Diabetes Association criteria where the 2-hour post-load glucose value is 2: 8.6 mmol/l.peer-reviewe

Quantum complementarity of microcavity polaritons

We present an experiment that probes polariton quantum correlations by exploiting quantum complementarity. Specifically, we find that polaritons in two distinct idler-modes interfere if and only if they share the same signal-mode so that "which-way" information cannot be gathered. The experimental results prove the existence of polariton pair correlations that store the "which-way" information. This interpretation is confirmed by a theoretical analysis of the measured interference visibility in terms of quantum Langevin equations

Thermodynamics and Excitations of Condensed Polaritons in Disordered Microcavities

We study the thermodynamic condensation of microcavity polaritons using a realistic model of disorder in semiconductor quantum wells. This approach correctly describes the polariton inhomogeneous broadening in the low density limit, and treats scattering by disorder to all orders in the condensed regime. While the weak disorder changes the thermodynamic properties of the transition little, the effects of disorder in the condensed state are prominent in the excitations and can be seen in resonant Rayleigh scattering.Comment: 5 pages, 3 eps figures (published version

Energy Relaxation in a 1-D Polariton Condensate

We study the kinetics of polariton condensation accounting for the condensation process as well as the energy relaxation of condensed polaritons due to their scattering with phonons and excitons. By assuming a Boltzmann kinetic description of the scattering process, we show that intra-condensate relaxation can be accounted for by an additional time-dependent term in the Gross-Pitaevskii equation. As an example, we apply the formalism to the experimental results recently obtained in polariton microwires [E. Wertz, et al., Nature Phys. 6, 860 (2010)]. In the presence of a local non-resonant optical pump, a dynamic balance between spatially dependent relaxation and particle loss develops and excites a series of modes, roughly equally spaced in energy. Upon comparison, excellent agreement is found with the experimental data.Comment: 6 pages, 4 figure

Report on the radiometric analysis of the Ghar Dalam fossil specimens prepared for the Ghar Dalam Museum

Uranium is a radioactive element emitting mainly alpha rays, but its daughter elements Th and Ra are gamma ray emitters. A high resolution gamma ray spectrometry system can be used to determine gamma-emitting radionuclides with energies ranging from 1 keV to 10 MeV depending on the type of detector in a large variety of sample matrices. The simultaneous detection of several gamma radionuclide emitters in the sample material was carried out with a coaxial germanium detector of high resolution connected to a multichannel analyser. Automatic processing of the collected spectral data was controlled by a computer system with selected software. Sources of error in the technique may be caused by improper spectral identities, changes in background, errors in calibration and/or geometry, and lack of homogeneity in samples. Since the samples tested were not in a standardised geometry, some variation in the readings could be expected due to the difference in sample homogeneity. The results obtained for the various samples were standardised as a ratio of 40K, on the assumption that the high solubility of potassium salts would result in a steady equilibrium in all samples. Several fossil specimens kept in the Ghar Dalam Museum were borrowed by courtesy of Dr. G. Zammit Maempel. The specimens had unfortunately no information as to the level they were excavated from, and their providence could not be reliably confirmed.peer-reviewe

Emergence of entanglement from a noisy environment: The case of polaritons

We show theoretically that polariton pairs with a high degree of polarization entanglement can be produced through parametric scattering. We demonstrate that it can emerge in coincidence experiments, even at low excitation densities where the dynamics is dominated by incoherent photoluminesce. Our analysis is based on a microscopic quantum statistical approach that treats coherent and incoherent processes on an equal footing, thus allowing for a quantitative assessment of the amount of entanglement under realistic experimental conditions. This result puts forward the robustness of pair correlations in solid-state devices, even when noise dominates one-body correlations.Comment: revised version. new figure

The new physics of non-equilibrium condensates: insights from classical dynamics

We discuss the dynamics of classical Dicke-type models, aiming to clarify the mechanisms by which coherent states could develop in potentially non-equilibrium systems such as semiconductor microcavities. We present simulations of an undamped model which show spontaneous coherent states with persistent oscillations in the magnitude of the order parameter. These states are generalisations of superradiant ringing to the case of inhomogeneous broadening. They correspond to the persistent gap oscillations proposed in fermionic atomic condensates, and arise from a variety of initial conditions. We show that introducing randomness into the couplings can suppress the oscillations, leading to a limiting dynamics with a time-independent order parameter. This demonstrates that non-equilibrium generalisations of polariton condensates can be created even without dissipation. We explain the dynamical origins of the coherence in terms of instabilities of the normal state, and consider how it can additionally develop through scattering and dissipation.Comment: 10 pages, 4 figures, submitted for a special issue of J. Phys.: Condensed Matter on "Optical coherence and collective phenomena in nanostructures". v2: added discussion of links to exact solution