67 research outputs found
Nonequilibrium Langevin Approach to Quantum Optics in Semiconductor Microcavities
Recently the possibility of generating nonclassical polariton states by means
of parametric scattering has been demonstrated. Excitonic polaritons propagate
in a complex interacting environment and contain real electronic excitations
subject to scattering events and noise affecting quantum coherence and
entanglement. Here we present a general theoretical framework for the realistic
investigation of polariton quantum correlations in the presence of coherent and
incoherent interaction processes. The proposed theoretical approach is based on
the {\em nonequilibrium quantum Langevin approach for open systems} applied to
interacting-electron complexes described within the dynamics controlled
truncation scheme. It provides an easy recipe to calculate multi-time
correlation functions which are key-quantities in quantum optics. As a first
application, we analyze the build-up of polariton parametric emission in
semiconductor microcavities including the influence of noise originating from
phonon induced scattering.Comment: some corrections in the presentation mad
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
Approximate computing design exploration through data lifetime metrics
When designing an approximate computing system, the selection of the resources to modify is key. It is important that the error introduced in the system remains reasonable, but the size of the design exploration space can make this extremely difficult. In this paper, we propose to exploit a new metric for this selection: data lifetime. The concept comes from the field of reliability, where it can guide selective hardening: the more often a resource handles "live" data, the more critical it be-comes, the more important it will be to protect it. In this paper, we propose to use this same metric in a new way: identify the less critical resources as approximation targets in order to minimize the impact on the global system behavior and there-fore decrease the impact of approximation while increasing gains on other criteria
Dynamics-Controlled Truncation Scheme for Nonlinear Dynamics in Semiconductor Microcavities
We present a systematic theory of Coulomb-induced correlation effects in the
nonlinear optical processes within the strong-coupling regime. In this paper we
shall set a dynamics controlled truncation scheme \cite{Axt Stahl} microscopic
treatment of nonlinear parametric processes in SMCs including the
electromagnetic field quantization. It represents the starting point for the
microscopic approach to quantum optics experiments in the strong coupling
regime without any assumption on the quantum statistics of electronic
excitations (excitons) involved. We exploit a previous technique, used in the
semiclassical context, which, once applied to four-wave mixing in quantum
wells, allowed to understand a wide range of observed phenomena \cite{Sham
PRL95}. We end up with dynamical equations for exciton and photon operators
which extend the usual semiclassical description of Coulomb interaction
effects, in terms of a mean-field term plus a genuine non-instantaneous
four-particle correlation, to quantum optical effects.Comment: preprint version, no figures an entire section adde
Monitoring stimulated emission at the single photon level in one-dimensional atoms
We theoretically investigate signatures of stimulated emission at the single
photon level for a two-level atom interacting with a one-dimensional light
field. We consider the transient regime where the atom is initially excited,
and the steady state regime where the atom is continuously driven with an
external pump. The influence of pure dephasing is studied, clearly showing that
these effects can be evidenced with state of the art solid state devices. We
finally propose a scheme to demonstrate the stimulation of one optical
transition by monitoring another one, in three-level one-dimensional atoms.Comment: 4 pages, 4 figures. Improved introduction; Comments adde
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