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Search Results: 1 - 10 of 200707 matches for " P.;Wasilewski "
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Multimode Raman light-atom interface in warm atomic ensemble as multiple three-mode quantum operations
Micha? Parniak,Daniel P?cak,Wojciech Wasilewski
Physics , 2015,
Abstract: We analyze the properties of a Raman quantum light-atom interface in long atomic ensemble and its applications as a quantum memory or two-mode squeezed state generator. We consider the weak-coupling regime and include both Stokes and anti-Stokes scattering and the effects of Doppler broadening in buffer gas assuming frequent velocity-averaging collisions. We find the Green functions describing multimode transformation from input to output fields of photons and atomic excitations. Proper mode basis is found via singular value decomposition for short interaction times. It reveals that triples of modes are coupled by a transformation equivalent to a combination of two beamsplitters and a two-mode squeezing operation. We analyze the possible transformations on an example of warm rubidium-87 vapor. The model we present bridges the gap between the Stokes only and anti-Stokes only interactions providing simple, universal description in a temporally and longitudinally multimode situation. Our results also provide an easy way to find an evolution of the states in a Schr\"odinger picture thus facilitating understanding and design.
Challenges for Polish Learners of English from the Implementing of Learning Strategies in the National Curriculum: A Report
Jacek Wasilewski
Humanising Language Teaching , 2010, DOI: 17559715
Contemporary Understanding of the Reading Process and Reading Strategies Used by ESOL Learners While Reading a Written Discourse
Jacek Wasilewski
Humanising Language Teaching , 2009,
A WIN-WIN Situation: Exploratory Language Learning and Teaching in a Foreign Language Classroom - Action Research Perspective
Jacek Wasilewski
Humanising Language Teaching , 2010, DOI: 17559715
Amalgamated direct sums of operator spaces
Mateusz Wasilewski
Mathematics , 2014,
Abstract: We consider amalgamated direct sums (and their dual counterparts -- fibre products) of operator spaces and study their behaviour with respect to different quantisations (minimal and maximal). We show examples of amalgamated direct sums of two $L^{\infty}$-spaces over a common subspace that are not minimal themselves, thus answering a question posed by Vern Paulsen.
Spin depolarization in quantum dots
Sachrajda, A.S.;Gould, C.;Hawrylak, P.;Feng, Y.;Zawadzki, P.;Wasilewski, Z.;
Brazilian Journal of Physics , 1999, DOI: 10.1590/S0103-97331999000400006
Abstract: we have performed single electron spectroscopy experiments on single lateral quantum dots. we demonstrate that the lateral nature of the tunneling as well as the properties of the 2deg leads can be used to extract new information in the 'spin-flip' regime. calculations confirm that one needs to go beyond the hartree-fock approximation and include correlation effects to explain the experimental observations. the results are found to be consistent with the presence of spin depolarization events at the 'spin-flips'.
Fractal Conductance Fluctuations in a Soft Wall Stadium and a Sinai Billiard
A. S. Sachrajda,R. Ketzmerick,C. Gould,Y. Feng,P. J. Kelly,A. Delage,Z. Wasilewski
Physics , 1997, DOI: 10.1103/PhysRevLett.80.1948
Abstract: Conductance fluctuations have been studied in a soft wall stadium and a Sinai billiard defined by electrostatic gates on a high mobility semiconductor heterojunction. These reproducible magnetoconductance fluctuations are found to be fractal confirming recent theoretical predictions of quantum signatures in classically mixed (regular and chaotic) systems. The fractal character of the fluctuations provides direct evidence for a hierarchical phase space structure at the boundary between regular and chaotic motion.
Exciton lifetime in InAs/GaAs quantum dot molecules
C. Bardot,M. Schwab,M. Bayer,S. Fafard,Z. Wasilewski,P. Hawrylak
Physics , 2005, DOI: 10.1103/PhysRevB.72.035314
Abstract: The exciton lifetimes $T_1$ in arrays of InAs/GaAs vertically coupled quantum dot pairs have been measured by time-resolved photoluminescence. A considerable reduction of $T_1$ by up to a factor of $\sim$ 2 has been observed as compared to a quantum dots reference, reflecting the inter-dot coherence. Increase of the molecular coupling strength leads to a systematic decrease of $T_1$ with decreasing barrier width, as for wide barriers a fraction of structures shows reduced coupling while for narrow barriers all molecules appear to be well coupled. The coherent excitons in the molecules gain the oscillator strength of the excitons in the two separate quantum dots halving the exciton lifetime. This superradiance effect contributes to the previously observed increase of the homogeneous exciton linewidth, but is weaker than the reduction of $T_2$. This shows that as compared to the quantum dots reference pure dephasing becomes increasingly important for the molecules.
Single-photon emission from the natural quantum dots in the InAs/GaAs wetting layer
T. Kazimierczuk,A. Golnik,P. Kossacki,J. Gaj,Z. Wasilewski,A. Babinski
Physics , 2011, DOI: 10.1103/PhysRevB.84.115325
Abstract: Time-resolved microphotoluminescence study is presented for quantum dots which are formed in the InAs/GaAs wetting layer. These dots are due to fluctuations of In composition in the wetting layer. They show spectrally sharp luminescence lines with a low spatial density. We identify lines related to neutral exciton and biexciton as well as trions. Exciton emission antibunching (second order correlation value of g^2(0)=0.16) and biexciton-exciton emission cascade prove non-classical emission from the dots and confirm their potential as single photon sources.
Microwave radiation induced magneto-oscillations in the longitudinal and transverse resistance of a two dimensional electron gas
S. A. Studenikin,M. Potemski,P. T. Coleridge,A. Sachrajda,Z. R. Wasilewski
Physics , 2003, DOI: 10.1016/j.ssc.2003.10.008
Abstract: We confirm the existance of magneto-resistance oscillations in a microwave-irradiated two-dimensional electron gas, first reported in a series of papers by Zhudov et al. and Mani et al. In our experiments, on a sample with a more moderate mobility, the microwave induced oscillations are observed not only in the longitudinal - but also in the transverse-resistance (Hall resistance). The phase of the oscillations is such that the decrease (increase) in the longitudinal resistance is accompanied by an increase (decrease) in the absolute value of the Hall resistance. We believe that these new results provide valuable new information to better understand the origin of this interesting phenomenon.
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