ORBi Collection: Physics
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Gas dissolution in antibubble dynamics
http://hdl.handle.net/2268/171465
Title: Gas dissolution in antibubble dynamics
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<br/>Author, co-author: scheid, benoit; zawala, jan; Dorbolo, StéphaneLeptogenesis with a dynamical seesaw scale
http://hdl.handle.net/2268/171273
Title: Leptogenesis with a dynamical seesaw scale
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<br/>Author, co-author: Aristizabal Sierra, Diego; Tortola, Maria; Valle, Jose; Vicente, Avelino
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<br/>Abstract: In the simplest type-I seesaw leptogenesis scenario right-handed neutrino annihilation processes are absent. However, in the presence of new interactions these processes are possible and can affect the resulting B-L asymmetry in an important way. A prominent example is provided by models with spontaneous lepton number violation, where the existence of new dynamical degrees of freedom can play a crucial role. In this context, we provide a model-independent discussion of the effects of right-handed neutrino annihilations. We show that in the weak washout regime, as long as the scattering processes remain slow compared with the Hubble expansion rate throughout the relevant temperature range, the efficiency can be largely enhanced, reaching in some cases maximal values. Moreover, the B-L asymmetry yield turns out to be independent upon initial conditions, in contrast to the ''standard'' case. On the other hand, when the annihilation processes are fast, the right-handed neutrino distribution tends to a thermal one down to low temperatures, implying a drastic suppression of the efficiency which in some cases can render the B-L generation mechanism inoperative.Reactor mixing angle from hybrid neutrino masses
http://hdl.handle.net/2268/171272
Title: Reactor mixing angle from hybrid neutrino masses
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<br/>Author, co-author: Aristizabal Sierra, Diego; de Medeiros Varzielas, Ivo
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<br/>Abstract: In terms of its eigenvector decomposition, the neutrino mass matrix (in the basis where the charged lepton mass matrix is diagonal) can be understood as originating from a tribimaximal dominant structure with small deviations, as demanded by data. If neutrino masses originate from at least two different mechanisms, referred to as "hybrid neutrino masses", the experimentally observed structure naturally emerges provided one mechanism accounts for the dominant tribimaximal structure while the other is responsible for the deviations. We demonstrate the feasibility of this picture in a fairly model-independent way by using lepton-number-violating effective operators, whose structure we assume becomes dictated by an underlying A4 flavor symmetry. We show that if a second mechanism is at work, the requirement of generating a reactor angle within its experimental range always fixes the solar and atmospheric angles in agreement with data, in contrast to the case where the deviations are induced by next-to-leading order effective operators. We prove this idea is viable by constructing an A4-based ultraviolet completion, where the dominant tribimaximal structure arises from the type-I seesaw while the subleading contribution is determined by either type-II or type-III seesaw driven by a non-trivial A4 singlet (minimal hybrid model). After finding general criteria, we identify all the ZN symmetries capable of producing such A4-based minimal hybrid models.Self broadening coefficients and improved line intensities for the n7 band of C2H4 near 10.5 mm, and impact on ethylene retrievals from Jungfraujoch solar spectra
http://hdl.handle.net/2268/170533
Title: Self broadening coefficients and improved line intensities for the n7 band of C2H4 near 10.5 mm, and impact on ethylene retrievals from Jungfraujoch solar spectra
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<br/>Author, co-author: Vander Auwera, Jean; Fayt, André; Tudorie, Marcela; Rotger - Languereau, Maud; Boudon, Vincent; Franco, Bruno; Mahieu, Emmanuel
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<br/>Abstract: Ethylene (ethene, C2H4) is a tropospheric pollutant on the Earth, also present as a by-product of methane photochemistry in the atmosphere of outer solar system bodies. Remote sensing of ethylene in the infrared range relies on the 10 mm region. This spectral range corresponds to the excitation of 7 modes of vibration of 12C2H4, 4 of which being infrared active (see Fig. 1 of [1]). The corresponding n10, n7, n4 and n12 bands are located near 826, 949, 1026 and 1442 cm-1, respectively [1]. Among these, the n7 band is the strongest, indeed used for remote sensing measurements of ethylene.
Relying on high-resolution Fourier transform infrared (FTIR) spectra recorded in Brussels, the present work involved extensive measurements of individual line intensities and self broadening coefficients for the n7 band of 12C2H4. Compared to the corresponding information available in the latest edition of the HITRAN spectroscopic database (HITRAN 2012 [2]), the measured line intensities were found to be higher by about 10 % for high J lines in the P branch and lower by about 5 % for high J lines of the R branch, varying between these two limits roughly linearly with the line positions. Test calculations performed in this work indicated that these discrepancies could result from the relative values of the transition moments of the n10, n7 and n12 bands used when the information provided in HITRAN was generated (the transition moment of the n4 band was set to zero). The measured self broadening coefficients exhibit a dependence on both J and Ka, which was modeled empirically. The spectroscopic information for ethylene available in HITRAN 2012 was modified to match the present observations. The impact of these modifications on retrievals of atmospheric ethylene was then evaluated via FTIR retrievals in the 949.0 – 952.0 cm-1 microwindow, from a subset of ground-based high-resolution FTIR solar spectra recorded at the Jungfraujoch station. The new line intensities were found to lead to a reduction of the measured total columns of ethylene by -4.1±0.1 %, compared to the use of HITRAN 2012.The origin of two-dimensional electron gases at oxide interfaces: insights from theory
http://hdl.handle.net/2268/170355
Title: The origin of two-dimensional electron gases at oxide interfaces: insights from theory
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<br/>Author, co-author: Bristowe, Nicholas; Ghosez, Philippe; Littlewood, P.B.; Artacho, E.
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<br/>Abstract: The response of oxide thin ﬁlms to polar discontinuities at interfaces and surfaces has generated enormous activity due to the variety of interesting effects that it gives rise to. A case in point is the discovery of the electron gas at the interface between LaAlO3 and SrTiO3, which has since been shown to be quasi-two-dimensional, switchable, magnetic and/or superconducting. Despite these ﬁndings, the origin of the two-dimensional electron gas is highly debated and several possible mechanisms remain. Here we review the main proposed mechanisms and attempt to model expected effects in a quantitative way with the ambition of better constraining what effects can/cannot explain the observed phenomenology. We do it in the framework of a phenomenological model constructed to provide an understanding of the electronic and/or redox screening of the chemical charge in oxide heterostructures. We also discuss the effect of intermixing, both conserving and not conserving the total stoichiometry.Modeling reaction-limited Ostwald ripening of supported Ni catalysts in presence of CO: the role of particle size distribution
http://hdl.handle.net/2268/170353
Title: Modeling reaction-limited Ostwald ripening of supported Ni catalysts in presence of CO: the role of particle size distribution
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<br/>Author, co-author: Gommes, Cédric; Munnik, Peter; de Jongh, Petra; de Jong, KrijnDoping-dependent band structure of LaAlO3/SrTiO3 interfaces by soft x-ray polarization-controlled resonant angle-resolved photoemission
http://hdl.handle.net/2268/170352
Title: Doping-dependent band structure of LaAlO3/SrTiO3 interfaces by soft x-ray polarization-controlled resonant angle-resolved photoemission
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<br/>Author, co-author: Cancellieri, C.; Reinle-Schmitt, M.L.; Kobayashi, M.; Strocov, V.N.; Willmott, P.R.; Fontaine, Denis; Ghosez, Philippe; Filippetti, A.; Delugas, P.; Fiorentini, V.
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<br/>Abstract: Polarization-controlled synchrotron radiation was used to map the electronic structure of buried conducting interfaces of LaAlO3/SrTiO3 in a resonant angle-resolved photoemission experiment. A strong polarization dependence of the Fermi surface and band dispersions is demonstrated, highlighting different Ti 3d orbitals involved in two-dimensional (2D) conduction. Measurements on samples with different doping levels reveal different band occupancies and Fermi-surface areas.The photoemission results are directly compared with advanced ﬁrst-principles calculations, carried out for different 3d-band ﬁlling levels connected with the 2D mobile carrier concentrations obtained from transport measurements, with indication of charge localization at the interface.Linear electro-optic effect in multiferroic BiFeO3 thin ﬁlms
http://hdl.handle.net/2268/170351
Title: Linear electro-optic effect in multiferroic BiFeO3 thin ﬁlms
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<br/>Author, co-author: Sando, D.; Hermet, Patrick; Allibe, J.; Bourderionnet, J.; Fusil, S.; Carrétéro, C.; Jacquet, E.; Mage, J.-C.; Dolfi, D.; Barthélémy, A.; Ghosez, Philippe; Bibes, M.
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<br/>Abstract: Multiferroics are materials with coexisting magnetic and ferroelectric orders, which show potential for electrically controlled spintronic devices. A common application of ferroelectrics is in electro-optical modulators exploiting their electric-field-dependent optical indices. The coupling of optical and magnetic degrees of freedom is attractive for designing multifunctional devices, but to date the electro-optical response of multiferroics has hardly been explored. Here we report a joint experimental and theoretical study of this effect in multiferroic BiFeO3 thin ﬁlms. We conﬁrm the large birefringence present in single crystals and determine the electro-optic coefﬁcients r13 and r33. We present approaches to increase the obtained coefﬁcients, for instance, by using tetragonal-like BiFeO3, and expand the potential of multiferroics to optical applications.Self broadening coefficients and improved line intensities for the ν7 band of ethylene near 10.5 µm, and impact on ethylene retrievals from Jungfraujoch spectra
http://hdl.handle.net/2268/169909
Title: Self broadening coefficients and improved line intensities for the ν7 band of ethylene near 10.5 µm, and impact on ethylene retrievals from Jungfraujoch spectra
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<br/>Author, co-author: Vander Auwera, J; Fayt, A; Tudorie, M; Rotger, M; Boudon, V; Franco, Bruno; Mahieu, Emmanuel
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<br/>Abstract: Relying on high-resolution Fourier transform infrared (FTIR) spectra, the present work involved extensive measurements of individual line intensities and self broadening coefficients for the nu7 band of 12C2H4. The measured self broadening coefficients exhibit a dependence on both J and Ka. Compared to the corresponding information available in the latest edition of the HITRAN spectroscopic database, the measured line intensities were found to be higher by about 10 % for high J lines in the P branch and lower by about 5 % for high J lines of the R branch, varying between these two limits roughly linearly with the line positions. The impact of the presently measured line intensities on retrievals of atmospheric ethylene in the 949.0-952.0 cm-1 microwindow was evaluated using a subset of ground-based high-resolution FTIR solar spectra recorded at the Jungfraujoch station. The use of HITRAN 2012 with line intensities modified to match the present measurements led to a systematic reduction of the measured total columns of ethylene by -4.1+/-0.1 %.External constraints on optical control strategies in molecular orientation and photofragmentation: role of zero-area fields
http://hdl.handle.net/2268/169737
Title: External constraints on optical control strategies in molecular orientation and photofragmentation: role of zero-area fields
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<br/>Author, co-author: Sugny, Dominique; Vranckx, Stéphane; Ndong, Mamadou; Atabek, Osman; Desouter, MichèleExternal constraints on optical control strategies in molecular orientation and photofragmentation: role of zero-area fields
http://hdl.handle.net/2268/169737
Title: External constraints on optical control strategies in molecular orientation and photofragmentation: role of zero-area fields
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<br/>Author, co-author: Sugny, Dominique; Vranckx, Stéphane; Ndong, Mamadou; Atabek, Osman; Desouter, MichèleExternal constraints on optical control strategies in molecular orientation and photofragmentation: role of zero-area fields
http://hdl.handle.net/2268/169737
Title: External constraints on optical control strategies in molecular orientation and photofragmentation: role of zero-area fields
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<br/>Author, co-author: Sugny, Dominique; Vranckx, Stéphane; Ndong, Mamadou; Atabek, Osman; Desouter, MichèleExternal constraints on optical control strategies in molecular orientation and photofragmentation: role of zero-area fields
http://hdl.handle.net/2268/169737
Title: External constraints on optical control strategies in molecular orientation and photofragmentation: role of zero-area fields
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<br/>Author, co-author: Sugny, Dominique; Vranckx, Stéphane; Ndong, Mamadou; Atabek, Osman; Desouter, MichèleThe two scenarios for quantum multifractality breakdown
http://hdl.handle.net/2268/169678
Title: The two scenarios for quantum multifractality breakdown
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<br/>Author, co-author: Georgeot, Bertrand; Dubertrand, Rémy; Garcia-Mata, Ignacio; Giraud, Olivier; Lemarié, Gabriel; Martin, John
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<br/>Abstract: Several types of physical systems are characterized by quantum wave func- tions with multifractal properties. In the quantum chaos field, they cor- respond to pseudointegrable systems, with properties intermediate between integrability and chaos. In condensed matter, they include electrons in a disordered potential at the Anderson metal-insulator transition. This multi- fractality leads to particular transport properties and appears in conjunction with specific types of spectral statistics. In parallel, progress in experimental techniques allows to observe finer and finer properties of the wavefunctions of quantum or wave systems, as well as to perform experiments with un- precedented control on the dynamics of the systems studied. In this context, this talk will discuss the robustness of multifractality in presence of footnote- size perturbations. We expose two scenarios for the breakdown of quantum multifractality under the effect of such perturbations. In the first scenario, multifractality survives below a certain scale of the quantum fluctuations. In the other one, the fluctuations of the wave functions are changed at every scale and each multifractal dimension smoothly goes to the ergodic value. We use as generic examples a one-dimensional dynamical system and the three- dimensional Anderson model at the metal-insulator transition, and show that for different types of perturbation the destruction of multifractal properties always follows one of these two ways. Our results thus suggest that quantum multifractality breakdown is universal and obeys one of these two scenarios depending on the perturbation. We also discuss the experimental implica- tions.Magnetic properties and anisotropy of orthorhombic DyMnO3 single crystal
http://hdl.handle.net/2268/169625
Title: Magnetic properties and anisotropy of orthorhombic DyMnO3 single crystal
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<br/>Author, co-author: Pękała, M.; Wolff-Fabris, F.; Fagnard, Jean-François; Vanderbemden, Philippe; Mucha, J.; Gospodinov, M. M.; Lovchinov, V.; Ausloos, Marcel
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<br/>Abstract: An orthorhombic DyMnO3 single crystal has been studied in magnetic fields up to 14 T and between 3 K and room temperature. The field dependent ordering temperature of Dy moments is deduced. The paramagnetic Curie Weiss behavior is related mainly to the Dy3+sublattice whereas the Mn sublattice contribution plays a secondary role. DC magnetization measurements show marked anisotropic features, related to the anisotropic structure of a cubic system stretched along a body diagonal, with a magnetic easy axis parallel to the crystallographic b axis. A temperature and field dependent spin flop transition is observed below 9 K, when relatively weak magnetocrystalline anisotropy is overcome by magnetic fields up to 1.6 T.Magnetocaloric effect of monovalent K doped manganites Pr0.6Sr0.4−xKxMnO3 (x=0 to 0.2)
http://hdl.handle.net/2268/169622
Title: Magnetocaloric effect of monovalent K doped manganites Pr0.6Sr0.4−xKxMnO3 (x=0 to 0.2)
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<br/>Author, co-author: Thaljaoui, R.; Boujelben, W.; Pękała, M.; Pękała, K.; Fagnard, Jean-François; Vanderbemden, Philippe; Donten, M.; Cheikhrouhou, A.
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<br/>Abstract: Magnetic and magnetocaloric properties are reported for polycrystalline monovalent potassium doped manganites Pr0.6Sr0.4−xKxMnO3 (x=0, 0.05, 0.1, 0.15 and 0.2) crystallized in orthorhombic structure with Pnma space group. The increasing K content shifts the paramagnetic to ferromagnetic transition temperature from 310 K for x=0 to 269 K for x=0.2. The magnetic entropy change under magnetic field variation of 2 T is found to be 1.95, 3.09, 2.89, 3.05 and 3.2 J/kgK for x varying from 0 to 0.2, respectively. The highest relative cooling power of 102 J/kg is observed for the undoped sample. The sensitivity of magnetic entropy change to magnetic field is estimated by a local N(T) exponent exhibiting the characteristic temperature variation. Phenomenological universal curves of entropy change and Arrott plots confirm the second order phase transition.Magnetic susceptibility and electron magnetic resonance study of monovalent potassium doped manganites Pr0.6Sr0.4−xKxMnO3
http://hdl.handle.net/2268/169619
Title: Magnetic susceptibility and electron magnetic resonance study of monovalent potassium doped manganites Pr0.6Sr0.4−xKxMnO3
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<br/>Author, co-author: Thaljaoui, R.; Pękała, K.; Pękała, M.; Boujelben, W.; Szydłowska, J.; Fagnard, Jean-François; Vanderbemden, Philippe; Cheikhrouhou, A.
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<br/>Abstract: The monovalent potassium doped manganites Pr0.6Sr0.4−xKxMnO3 (x = 0.05–0.2) are characterized using the complementary magnetic susceptibility and electron resonance methods. In paramagnetic phase the temperature variations of the inverse magnetic susceptibility and the inverse intensity of resonance signal obey the Curie–Weiss law. A similarity in temperature variation of resonance signal width and the adiabatic polaron conductivity points to the polaron mechanism controlling the resonance linewidth. The low temperature limit of the pure paramagnetic phase is determined from the electron resonance spectra revealing the mixed phase spread down to the Curie temperature.Structural, magnetic and magneto-transport properties of monovalent doped manganite Pr0.55K0.05Sr0.4MnO3
http://hdl.handle.net/2268/169607
Title: Structural, magnetic and magneto-transport properties of monovalent doped manganite Pr0.55K0.05Sr0.4MnO3
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<br/>Author, co-author: Thaljaoui, R.; Boujelben, W.; Pękała, M.; Pękała, K.; Antonowicz, J.; Fagnard, Jean-François; Vanderbemden, Philippe; Dąbrowska, S.; Mucha, J.
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<br/>Abstract: Pr0.55K0.05Sr0.4MnO3 sample have been synthesized using the conventional solid state reaction. Rietveld refinements of the X-ray diffraction patterns at room temperature confirm that the sample is single phase and crystallizes in the orthorhombic structure with Pnma space group; the crystallite size is around 70 nm. The SEM images show that grain size spreads around 1000–1200 nm. DTA analysis does not reveal any clear transition in temperature range studied. The low-temperature DSC indicates that Curie temperature is around 297 K. Magnetization measurements in a magnetic applied field of 0.01 T exhibit a paramagnetic–ferromagnetic transition at the Curie temperature TC = 303 K. A magnetic entropy change under an applied magnetic field of 2 T is found to be 2.26 J kg−1 K−1, resulting in a large relative cooling power around 70 J/kg. Electrical resistivity measurements reveal a transition from semiconductor to metallic phase. The thermal conductivity is found to be higher than that reported for undoped and Na doped manganites reported by Thaljaoui et al. (2013).Generation of artificial magnetic fields using dipole-dipole interactions
http://hdl.handle.net/2268/169604
Title: Generation of artificial magnetic fields using dipole-dipole interactions
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<br/>Author, co-author: Cesa, Alexandre; Martin, John
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<br/>Abstract: In 1996, Lloyd [1] showed that the dynamics of complex many-body quantum systems can be efficiently simulated by quantum computers, an idea first put forward by Manin [2] and further developed by Feynman [3]. Although the first quantum computers of a few qubits have been realised experimentally [4, 5], the advent of scalable quantum computers might take another few decades. An alternative tool in the context of simulation is a highly controllable quantum system able to mimic the dynamics of other complex quantum systems, known as an analog quantum simulator. Cold neutral atoms and trapped ions have been shown to be versatile quantum simulators [6, 7] thanks to their high flexibility, controllability, and scalability. They permit one to study a wide range of problems arising from atomic physics, relativistic quantum physics, or cosmology [8]. Since neutral atoms do not carry any net charge, the simulation of electric and magnetic condensed matter phenomena, such as the spin Hall effect, seems out of reach. To overcome this apparent difficulty, the idea has been proposed to create artificial electromagnetic potentials for neutral atoms based on atom-light interaction [9– 12]. These artificial potentials act on neutral atoms as real electromagnetic potentials act on charged particles. Many works on artificial gauge potentials induced by atom-light interactions adopt a single-particle approach [12]. The predicted potentials are then supposed to be valid for a system of weakly interacting atoms. So far, the consequences of atom-atom interactions on the generation of artificial gauge fields has little been studied. The aim of this work is to study the artificial gauge fields arising from the interaction of two Rydberg atoms driven by a common laser field [13]. In this situation, we show that the combined atom-atom and atom-field interactions give rise to nonuniform, artificial gauge potentials. We identify the mechanism responsible for the emergence of these gauge potentials. Analytical expressions for the latter indicate that the strongest artificial magnetic fields are reached in the regime intermediate between the dipole blockade regime and the regime in which the atoms are sufficiently far apart such that atom-light interaction dominates over atom-atom interactions. We discuss the differences and similarities of artificial gauge fields originating from resonant dipole-dipole [14] and van der Waals [15] interactions. We also give an estimation of experimentally attainable artificial magnetic fields resulting from this mechanism and we discuss their detection through the deflection of the atomic motion.
[1] S. Lloyd, Science 273, 1073 (1996).
[2] Yu. I. Manin, Computable and uncomputable, Sovetskoye Radio, Moscow, 1980.
[3] R. P. Feynman, Int. J. Theor. Phys. 21, 467 (1982).
[4] L. DiCarlo, J. M. Chow, J. M. Gambetta, Lev S. Bishop, B. R. Johnson, D. I. Schuster, J. Majer, A. Blais, L. Frunzio, S. M. Girvin, and R. J. Schoelkopf, Nature 460, 240 (2009). [5] N. Xu, J. Zhu, D. Lu, X. Zhou, X. Peng, and J. Du, Phys. Rev. Lett. 108, 130501 (2012).
[6] I. Buluta and F. Nori, Science 326, 108 (2009).
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[10] G. Juzeliunas, P. Öhberg, J. Ruseckas, and A. Klein, Phys. Rev. A 71, 053614 (2005).
[11] G. Juzeliunas, J. Ruseckas, P. Öhberg, and M. Fleischhauer, Phys. Rev. A 73, 025602 (2006).
[12] J. Dalibard, F. Gerbier, G. Juzeliu ̄nas, and P. Öhberg, Rev. Mod. Phys. 83, 1523 (2011).
[13] A. Cesa and J. Martin, Phys. Rev. A 88,062703 (2013). [14] A. Gaëtan, Y. Miroshnychenko, T. Wilk, A. Chotia, M. Viteau, D. Comparat, P. Pillet, A. Browaeys, and P. Grangier, Nature Physics 5, 115 (2009).
[15] L. Béguin, A. Vernier, R. Chicireanu, T. Lahaye, and A. Browaeys, Phys. Rev. Lett. 110, 263201 (2013).Alteration of decoherence-free states caused by dipole-dipole interactions
http://hdl.handle.net/2268/169599
Title: Alteration of decoherence-free states caused by dipole-dipole interactions
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<br/>Author, co-author: Damanet, François; Martin, John
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<br/>Abstract: Decoherence, known as the consequence of the coupling of any quantum system to its environment, causes information loss in the system and represents a major problem in the physical realization of quantum computers [1]. Decoherence-Free States (DFS) are considered as a possible solution to this problem. A set of trapped cold atoms placed in a DFS state will be immune against decoherence due to spontaneous emission. However, because of dipole-dipole interactions between atoms, induced dephasing effects are likely to destroy the coherence and drive the system out of its DFS [1, 2]. In this work, we study numerically the dynamics of a set of two-level atoms initially in a DFS with respect to dissipative processes by solving the master equation including both dissipative dynamics and dipole dipole interactions. We fo- cus our attention on the infuence of dipolar coupling on the radiated energy rate and coherence of the system as in [3]. In particular, by averaging over many realizations of close randomly distributed atomic positions, we show the formation of a superradiant-like pulse and we study its properties as a function of the dipolar coupling strength.
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[3] W. Feng, Y. Li & S-Y. Zhu, Phys. Rev. A 88, 033856 (2013).