Signatures of the Optical Stark Effect on Entangled Photon Pairs from Resonantly-Pumped Quantum Dots

Two-photon resonant excitation of the biexciton-exciton cascade in a quantum dot generates highly polarization-entangled photon pairs in a near-deterministic way. However, there are still open questions on the ultimate level of achievable entanglement. Here, we observe the impact of the laser-induced AC-Stark effect on the spectral emission features and on entanglement. A shorter emission time, longer laser pulse duration, and higher pump power all result in lower values of concurrence. Nonetheless, additional contributions are still required to fully account for the observed below-unity concurrence.Comment: 7 pages, 3 figure

Ogrzewanie powietrza przepływającego w kanałach w systemach z indywidualnym dostarczaniem powietrza do pomieszczenia

Derived is the equation to calculate the heating of an air stream along the channels. It can he used to more accurately calculate the heating of an air stream. An example illustrates the use of the derived formula

Mathematical Description of Heat Transfer and Air Movement Processes in Convectional Elements of a Building's Passive Solar Heating Systems

AbstractThe article discusses convectional elements of a building's passive solar heating systems. Mathematical description of heat transfer and air movement processes in the convection elements is presented as an equation set in differential form. The set of equations allows the determination of the temperature distribution in the convectional element as well as the heat flow being supplied into the room. At the same time, it is possible to analyze structural factors influencing the heat flow. The mathematical description of the heat transfer and air movement processes is illustrated by examples of calculations and diagrams of air movement in the convectional elements

Strain-tuning of the optical properties of semiconductor nanomaterials by integration onto piezoelectric actuators

39 pags., 27 figs. -- Open Access funded by Creative Commons Atribution Licence 3.0The tailoring of the physical properties of semiconductor nanomaterials by strain has been gaining increasing attention over the last years for a wide range of applications such as electronics, optoelectronics and photonics. The ability to introduce deliberate strain fields with controlled magnitude and in a reversible manner is essential for fundamental studies of novel materials and may lead to the realization of advanced multi-functional devices. A prominent approach consists in the integration of active nanomaterials, in thin epitaxial films or embedded within carrier nanomembranes, onto Pb(MgNb)O-PbTiO-based piezoelectric actuators, which convert electrical signals into mechanical deformation (strain). In this review, we mainly focus on recent advances in strain-tunable properties of self-assembled InAs quantum dots (QDs) embedded in semiconductor nanomembranes and photonic structures. Additionally, recent works on other nanomaterials like rare-earth and metal-ion doped thin films, graphene and MoS or WSe semiconductor two-dimensional materials are also reviewed. For the sake of completeness, a comprehensive comparison between different procedures employed throughout the literature to fabricate such hybrid piezoelectric-semiconductor devices is presented. It is shown that unprocessed piezoelectric substrates (monolithic actuators) allow to obtain a certain degree of control over the nanomaterials' emission properties such as their emission energy, fine-structure-splitting in self-assembled InAs QDs and semiconductor 2D materials, upconversion phenomena in BaTiO thin films or piezotronic effects in ZnS:Mn films and InAs QDs. Very recently, a novel class of micro-machined piezoelectric actuators have been demonstrated for a full control of in-plane stress fields in nanomembranes, which enables producing energy-tunable sources of polarization-entangled photons in arbitrary QDs. Future research directions and prospects are discussed.This work was financially supported by European Union's Horizon 2020 research and innovation programme (SPQRel grant agreement no. 679183), European Union Seventh Framework Programme (FP7/2007–2013) under grant agreement no. 601126 (HANAS) and Austrian Science Fund (FWF): P 29603.Peer Reviewe

Evaluating recharge estimates based on groundwater head from different lumped models in Europe

Study region: The study uses 78 groundwater head time series across 10 European countries with various geological and hydrological settings. Study focus: The estimation of groundwater recharge using time series analysis and lumped modelling based on groundwater head time series is a low-cost and practical method. However, lumped recharge estimation models based on groundwater level variations are uncertain, and successful applications are known to depend on both climate and hydrogeological setting. Here, we assess the suitability of three different models to estimate recharge (Metran - Transfer Function-Noise model, AquiMod - groundwater level driven hydrological model, and GARDÉNIA - lumped catchment model). New hydrological insights: Results showed that while all three models generally did well during the modelling of groundwater heads, the resulting recharge estimations from the models were different. The analysis showed that the transfer-noise modelling of groundwater heads with recharge and evapotranspiration in Metran is not generally applicable for recharge estimation. The addition of physical information in AquiMod improved the recharge estimations, but the reliability was still limited without control of the water balance due to non-uniqueness. By adding discharge information to the modelling, GARDÉNIA can provide more reliable recharge values. Thus, recharge estimation from groundwater head time series without water balance information must be considered uncertain with low precision, but applicability can be improved when including knowledge of the local system