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Author: David Ananikian
Publisher:
ISBN: 9781109967159
Category : Bose-Einstein condensation
Languages : en
Pages : 102
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Book Description
At zero temperature the dynamics of the trapped BEC is well described by the Gross-Pitaevskii equation. Our primary goal is to explore the range of validity of a two-mode model in the basis of symmetric and antisymmetric eigenfunctions of the stationary Gross-Pitaevskii equation. In what we call an "improved two-mode model" (I2M), the tunneling coupling energy includes a non-linear term explicitly. We show that when the atom number in each well varies appreciably with time, the nonlinear interaction term produces a temporal change in the tunneling energy or rate. The usefulness of this model is demonstrated by good agreement with recent experimental results for the tunneling oscillation frequency. Especially for larger values of the nonlinear interaction term, the I2M model produces better agreement as compared to the models which have no interaction term in the tunneling energy and fail in the case of large effective coupling constant. In addition, we develop a multimode approach in contrast to Bogoliubov quasiparticle excitation theory. Compared to the I2M model the multimode approach has better agreement with the numerical solution of time-dependent Gross-Pitaevskii equation. A quantum I2M model has been introduced to obtain modified equations of motion for the second quantized version of BEC in the double-well potential. The dynamics of quantum I2M model is essentially governed by the su (2) subalgebra of the full dynamic algebra so (3,2) built on two types of creation and annihilation bose operators. We also extend our results for the case of nonzero temperature in the regime of partial local equilibrium between the condensate and noncondensate atoms deriving equations of motion for the damping oscillations. This approach is based on ZNG theory within the two-mode approximation which treats the noncondensate atoms statically. We analytically elaborate two different regimes: the small oscillation regime about zero imbalance between two wells, and the self-trapping regime about a metastable state with nonzero imbalance.
Author: David Ananikian
Publisher:
ISBN: 9781109967159
Category : Bose-Einstein condensation
Languages : en
Pages : 102
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Book Description
At zero temperature the dynamics of the trapped BEC is well described by the Gross-Pitaevskii equation. Our primary goal is to explore the range of validity of a two-mode model in the basis of symmetric and antisymmetric eigenfunctions of the stationary Gross-Pitaevskii equation. In what we call an "improved two-mode model" (I2M), the tunneling coupling energy includes a non-linear term explicitly. We show that when the atom number in each well varies appreciably with time, the nonlinear interaction term produces a temporal change in the tunneling energy or rate. The usefulness of this model is demonstrated by good agreement with recent experimental results for the tunneling oscillation frequency. Especially for larger values of the nonlinear interaction term, the I2M model produces better agreement as compared to the models which have no interaction term in the tunneling energy and fail in the case of large effective coupling constant. In addition, we develop a multimode approach in contrast to Bogoliubov quasiparticle excitation theory. Compared to the I2M model the multimode approach has better agreement with the numerical solution of time-dependent Gross-Pitaevskii equation. A quantum I2M model has been introduced to obtain modified equations of motion for the second quantized version of BEC in the double-well potential. The dynamics of quantum I2M model is essentially governed by the su (2) subalgebra of the full dynamic algebra so (3,2) built on two types of creation and annihilation bose operators. We also extend our results for the case of nonzero temperature in the regime of partial local equilibrium between the condensate and noncondensate atoms deriving equations of motion for the damping oscillations. This approach is based on ZNG theory within the two-mode approximation which treats the noncondensate atoms statically. We analytically elaborate two different regimes: the small oscillation regime about zero imbalance between two wells, and the self-trapping regime about a metastable state with nonzero imbalance.
Author: Tarik Berrada
Publisher: Springer
ISBN: 3319272330
Category : Science
Languages : en
Pages : 244
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Book Description
This thesis demonstrates a full Mach–Zehnder interferometer with interacting Bose–Einstein condensates confined on an atom chip. It relies on the coherent manipulation of atoms trapped in a magnetic double-well potential, for which the author developed a novel type of beam splitter. Particle-wave duality enables the construction of interferometers for matter waves, which complement optical interferometers in precision measurement devices, both for technological applications and fundamental tests. This requires the development of atom-optics analogues to beam splitters, phase shifters and recombiners. Particle interactions in the Bose–Einstein condensate lead to a nonlinearity, absent in photon optics. This is exploited to generate a non-classical state with reduced atom-number fluctuations inside the interferometer. This state is then used to study the interaction-induced dephasing of the quantum superposition. The resulting coherence times are found to be a factor of three longer than expected for coherent states, highlighting the potential of entanglement as a resource for quantum-enhanced metrology.
Author: Kaspar Sakmann
Publisher: Springer Science & Business Media
ISBN: 3642228666
Category : Science
Languages : en
Pages : 135
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Book Description
At extremely low temperatures, clouds of bosonic atoms form what is known as a Bose-Einstein condensate. Recently, it has become clear that many different types of condensates -- so called fragmented condensates -- exist. In order to tell whether fragmentation occurs or not, it is necessary to solve the full many-body Schrödinger equation, a task that remained elusive for experimentally relevant conditions for many years. In this thesis the first numerically exact solutions of the time-dependent many-body Schrödinger equation for a bosonic Josephson junction are provided and compared to the approximate Gross-Pitaevskii and Bose-Hubbard theories. It is thereby shown that the dynamics of Bose-Einstein condensates is far more intricate than one would anticipate based on these approximations. A special conceptual innovation in this thesis are optimal lattice models. It is shown how all quantum lattice models of condensed matter physics that are based on Wannier functions, e.g. the Bose/Fermi Hubbard model, can be optimized variationally. This leads to exciting new physics.
Author: Jaclyn Semple
Publisher:
ISBN:
Category :
Languages : en
Pages : 212
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Book Description
We numerically solve the Gross-Pitaevskii equation and the Bogoliubov de Gennes equations for a double well potential in order to model the dynamics of a Bose-Einstein condensate in a Josephson junction. First, the two dynamical regimes of the Josephson junction, that is, Josephson oscillations and self-trapping, are investigated under the application of a large sudden perturbation. It is found that the Josephson dynamics have a strong dependence on the strength of the interatomic interaction, and we observe the breakdown of the two-mode approximation. Second, we study the control of the dynamics through the use of a time-dependent, tilted double well potential. In the context of complete population transfer, the effect of the interactions on the adiabaticity and self-trapping is discussed in terms of a Landau-Zener-like model. We then explore the splitting of the condensate and the resulting dynamical behaviour by keeping the interaction strength constant, but changing the rate of the tilt sweep. Lastly, we examine the effect of the tilt sweep rate on the dynamics of population transfer. We observe a dependence of the self-trapping on the adiabaticity.
Author: Tim Langen
Publisher: Springer
ISBN: 3319185640
Category : Science
Languages : en
Pages : 154
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Book Description
This work presents a series of experiments with ultracold one-dimensional Bose gases, which establish said gases as an ideal model system for exploring a wide range of non-equilibrium phenomena. With the help of newly developed tools, like full distributions functions and phase correlation functions, the book reveals the emergence of thermal-like transient states, the light-cone-like emergence of thermal correlations and the observation of generalized thermodynamic ensembles. This points to a natural emergence of classical statistical properties from the microscopic unitary quantum evolution, and lays the groundwork for a universal framework of non-equilibrium physics. The thesis investigates a central question that is highly contested in quantum physics: how and to which extent does an isolated quantum many-body system relax? This question arises in many diverse areas of physics, and many of the open problems appear at vastly different energy, time and length scales, ranging from high-energy physics and cosmology to condensed matter and quantum information. A key challenge in attempting to answer this question is the scarcity of quantum many-body systems that are both well isolated from the environment and accessible for experimental study.
Author: Philippe Blanchard
Publisher: Springer Science & Business Media
ISBN: 0817682023
Category : Science
Languages : en
Pages : 223
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Book Description
This volume explores multiscale methods as applied to various areas of physics and to the relative developments in mathematics. In the last few years, multiscale methods have lead to spectacular progress in our understanding of complex physical systems and have stimulated the development of very refined mathematical techniques. At the same time on the experimental side, equally spectacular progress has been made in developing experimental machinery and techniques to test the foundations of quantum mechanics.
Author: Tim Byrnes
Publisher: Cambridge University Press
ISBN: 1108982115
Category : Science
Languages : en
Pages : 291
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Book Description
The rapid development of quantum technologies has driven a revolution in related research areas such as quantum computation and communication, and quantum materials. The first prototypes of functional quantum devices are beginning to appear, frequently created using ensembles of atoms, which allow the observation of sensitive, quantum effects, and have important applications in quantum simulation and matter wave interferometry. This modern text offers a self-contained introduction to the fundamentals of quantum atom optics and atomic many-body matter wave systems. Assuming a familiarity with undergraduate quantum mechanics, this book will be accessible for graduate students and early career researchers moving into this important new field. A detailed description of the underlying theory of quantum atom optics is given, before development of the key, quantum, technological applications, such as atom interferometry, quantum simulation, quantum metrology, and quantum computing.
Author: Christian Groß
Publisher: Springer Science & Business Media
ISBN: 3642256376
Category : Science
Languages : en
Pages : 123
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Book Description
Interferometry, the most precise measurement technique known today, exploits the wave-like nature of the atoms or photons in the interferometer. As expected from the laws of quantum mechanics, the granular, particle-like features of the individually independent atoms or photons are responsible for the precision limit, the shot noise limit. However this “classical” bound is not fundamental and it is the aim of quantum metrology to overcome it by employing entanglement among the particles. This work reports on the realization of spin-squeezed states suitable for atom interferometry. Spin squeezing was generated on the basis of motional and spin degrees of freedom, whereby the latter allowed the implementation of a full interferometer with quantum-enhanced precision.
Author: S. Lakshmibala
Publisher: Springer Nature
ISBN: 3031194144
Category : Science
Languages : en
Pages : 138
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Book Description
This book explores interesting possibilities of extracting information about quantum states from data readily obtained from experiments, such as tomograms and expectation values of appropriate observables. The procedures suggested for identifying nonclassical effects such as wave packet revivals, squeezing and entanglement solely from tomograms circumvent detailed state reconstruction. Several bipartite entanglement indicators are defined based on tomograms, and their efficacy assessed in models of atom-field interactions and qubit systems. Tools of classical ergodic theory such as time series and network analysis are applied to quantum observables treated as dynamical variables. This brings out novel aspects involving different time scales. The book is aimed at researchers in the areas of quantum optics and quantum dynamics.
Author:
Publisher: ScholarlyEditions
ISBN: 1464963282
Category : Science
Languages : en
Pages : 8864
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Book Description
Issues in General Physics Research / 2011 Edition is a ScholarlyEditions™ eBook that delivers timely, authoritative, and comprehensive information about General Physics Research. The editors have built Issues in General Physics Research: 2011 Edition on the vast information databases of ScholarlyNews.™ You can expect the information about General Physics Research in this eBook to be deeper than what you can access anywhere else, as well as consistently reliable, authoritative, informed, and relevant. The content of Issues in General Physics Research: 2011 Edition has been produced by the world’s leading scientists, engineers, analysts, research institutions, and companies. All of the content is from peer-reviewed sources, and all of it is written, assembled, and edited by the editors at ScholarlyEditions™ and available exclusively from us. You now have a source you can cite with authority, confidence, and credibility. More information is available at http://www.ScholarlyEditions.com/.
