Quantum Complementarity of Microcavity Polaritons

EPL (Europhysics Letters), 2009

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.

Polariton-induced optical asymmetry in the reflectivity spectra of coupled semiconductor microcavity structures, containing quantum wells in one of the cavities, is reported. The central mode of the system is only observable when viewed from one side of the structure, but is dark and invisible from the other side. At the same time, all other spectral features are the same from both sides of the structure. Microscopically, interference between the exciton and cavity modes is shown to lead to the optical asymmetry. Furthermore, the asymmetric exciton-cavity mode is observable only for light incident on the cavity without excitons, a result shown to be fully consistent with a coupled oscillator model.

Physical Review B, 2014

We study the polarisation-dependent polariton-polariton interaction through its effect on a parametric scattering process in a microcavity (MC). The ratio of the anti-circular interaction strength V2 over its co-circular counterpart V1 is involved in defining the regime in which many nonlinear processes arise in MCs, such as parametric conversion or condensation. We measure the ratio V2/V1 using a stimulated energy-degenerate parametric scattering process in a multiple MC. The sample is pumped at normal incidence, probed with a non-zero angle, and the phase-matched idler is observed at the opposite angle. The idler behaviour, both in power and polarisation, is compared to a hamiltonian interaction model that takes into account the two polarisation-dependent parametric scattering channels characterized by V1 and V2. The proposed method to measure the ratio V2/V1 is convenient and precise. The flexibility of the triple MC allows to observe the process and measure this ratio over a large range of detunings, where we find it to be highly dependent on the detuning. These measurements complement the previous study of Vladimirova et al. [Phys. Rev. B 82, 075301 (2010)] with an original approach and for detunings that were unexplored up to now.

2010

de l'orientation des spins des polaritons. Sous excitation polarisée linéairement, la bistabilité est fortement réduite, voire supprimée. Nous montrons que cela est dûà un appariement des polaritons de spin opposés pour former des biexcitons. Nous démontrons le contrôle des différents régimes d'instabilité optiqueà travers la polarisation de l'excitation. Nous regardons ensuite le cas des polaritons confinés. En travaillant avec un uniqueétat confiné, nous obtenons un contrôle optique complet des interactions de spin entre polaritons. Nous démontrons pour la première fois la multistabilité d'un ensemble cohérent de spins dans l'état solide. Ce résultat est uneétape importante dans le cadre de la recherche sur la manipulation de spins pour le développement de dispositifs optoélectroniques. Finalement, nous montrons l'impact que pourrait avoir le spin des polaritons sur le couplage en polaritons de dimensionnalités différentes ainsi que sur le contrôle des régimes de propagation des fluides de polaritons. Nos expériences sont appuyées par des modèles théoriques. Nous proposons, en perspective, de nouvelles expériences sur la dynamique des polaritons et sur la manipulation cohérente de spins dans les microcavités.

2016

Polaritons are quasi-particles originating from the coupling of light with matter that demonstrated quantum phenomena at the many-particle mesoscopic level, such as BEC and superfluidity. A highly sought and long-time missing feature of polaritons is a genuine quantum manifestation of their dynamics at the single-particle level. Although they are conceptually perceived as entangled states and theoretical proposals abound for an explicit manifestation of their single-particle properties, so far their behaviour has remained fully accountable for by classical and mean-field theories. In this Article, we report the first experimental demonstration of a genuinely-quantum manifestation of microcavity polaritons, by swapping, in a two-photon entangled state generated by parametric down-conversion, a photon for a polariton. Furthermore, we show how single polaritons are affected by polariton-polariton interactions in a propaedeutic demonstration of their qualities for quantum information ap...

Physical Review A, 2003

We explore the behaviour of a system which consists of a photon mode dipole coupled to a medium of two-level oscillators in a microcavity in the presence of decoherence. We consider two types of decoherence processes which are analogous to magnetic and non-magnetic impurities in superconductors. We study different phases of this system as the decoherence strength and the excitation density is changed. For a low decoherence we obtain a polariton condensate with comparable excitonic and photonic parts at low densities and a BCS-like state with bigger photon component due to the fermionic phase space filling effect at high densities. In both cases there is a large gap in the density of states. As the decoherence is increased the gap is broadened and suppressed, resulting in a gapless condensate and finally a suppression of the coherence in a low density regime and a laser at high density limit. A crossover between these regimes is studied in a self-consistent way analogous to the Abrikosov and Gor'kov theory of gapless superconductivity.

physica status solidi (c), 2005

PACS 42.50.Pq, 71.35.Cc, Polarization selective polariton scattering is demonstrated in quasi-one-dimensional microcavities. Due to the reduced symmetry in wire shaped cavities each polariton mode shows a polarization splitting into two modes polarized along and perpendicular to the wire axis. For a given detunig, energy conservation can be fulfilled for parametric scattering among modes of different polarization. The characteristics of this process are analyzed.

Applied Physics …, 2011

Replacing independent single quantum wells inside a strongly-coupled semiconductor microcavity with double quantum wells produces a special type of polariton. Using asymmetric double quantum wells in devices processed into mesas allows the alignment of the electron levels to be voltagetuned. At the resonant electronic tunnelling condition, we demonstrate that 'oriented polaritons' are formed, which possess greatly enhanced dipole moments. Since the polariton-polariton scattering rate depends on this dipole moment, such devices could reach polariton lasing, condensation and optical nonlinearities at much lower threshold powers.

Physics Letters A, 2012

Diamagnetism of condensed microcavity polaritons in a vertically applied magnetic field is theoretically studied by using the density of free energy of polaritons. The magnetic dependence of polariton-polariton interactions and spin polarization degree of polaritons are derived, and are used to show the diamagnetic behavior of the polariton spin polarization, which is discussed for GaAs-based microcavities. We show that for strong magnetic field the spin polarization of the polaritons is paramagnetic as usual, while around positive exciton-photon detuning and special Rabi splitting, the spin polarization of the polaritons could be diamagnetic. In addition, weak magnetic field and high polariton density are beneficial to observe the polariton diamagnetism.

Superlattices and Microstructures, 1999

We present coherent control experiments which simultaneously probe both the coherence and the population dynamics of the exciton-photon polariton states in a semiconductor microcavity. The coherent manipulation of either the spin orientation or the density of polaritons is demonstrated leading to the measurement of the optical dephasing time. The polariton scattering by acoustical phonons or by mutual collision processes are investigated by a simultaneous measurement of both the optical dephasing time T 2 and the decay time T 1 of the radiant states. These results clearly evidence a quenching of the different scattering processes at resonance.