Many-Body Effects in a Model of Electromagnetically Induced Transparency

We study the effect of inter-band interactions in the absorption profile of a semi-classical model describing electromagnetically induced transparency. We develop a consistent approach using a non-hermitian Hamiltonian to model particle decay. This allow us to characterize the system response for different number of particles so that the effect of particle-interaction on the transmission profile can be studied over a wide range of characteristic parameters.Comment: 5+ pages, 4 figure

End-to-end entanglement in Bose-Hubbard chains

We study the ground state as well as the dynamics of chains of bosons with local repulsive interactions and nearest-neighbour exchange using numerical techniques based on density matrix decimation. We explore the development of entanglement between the terminal sites of such chains as mechanisms are invoked to concentrate population in these sites. We find that long-range entanglement in the ground state emerges as a result of hopping taking place at the whole chain length in systems with appropriate hopping coefficients. Additionally, we find appropriate perturbations to increase the entanglement between the end sites above their ground state values.Comment: 7 pages, 8 figure

Thermalization of linear Fermi systems

The issue of thermalization in open quantum systems is explored from the perspective of fermion models with quadratic couplings and linear baths. Both the thermodynamic state and the stationary solution of the Lindblad equation are rendered as a matrix-product sequence following a reformulation in terms of underlying algebras, allowing to characterize a family of stationary solutions and determine the cases where they correspond to thermal states. This characterization provides insight into the operational mechanisms that lead the system to thermalization and their interplay with mechanisms that tend to drive it out of thermal equilibrium.Comment: 10 pages, 2 figures, Comments or suggestions are always welcom

Quantum Effects In Low Temperature Bosonic Systems

In the first part, we investigate the effect of long range particle exchange in ideal bosonic chains. We establish that by using the Heisenberg formalism along with matrix product state representation we can study the evolution as well as the ground state of bosonic arrangements while including terms beyond next-neighbour hopping. The method is then applied to analyse the quench dynamics of condensates in a trapping potential and also to study the emergence of entanglement as a result of collision in boson chains. In the second part, we study the ground state as well as the dynamics of 1D boson arrangements with local repulsive interactions and nearest-neighbour exchange using numerical techniques based on time evolving block decimation (TEBD). We focus on the development of quantum correlations between the terminal places of these arrangements. We find that long-range entanglement in the ground state arises as a result of intense boson tunnelling taking place across the whole chain in systems with appropriate hopping coefficients. Additionally, we identify the perturbations necessary to increase the entanglement between the end sites above their ground state values. In the final part, we study the wave function of a kicked condensate using a perturbative approach and compare the results obtained in this way with numerical simulations.Comment: Ph.D. Thesi

Classical Dynamics of Quantum Entanglement

We numerically analyze the dynamical generation of quantum entanglement in a system of 2 interacting particles, started in a coherent separable state, for decreasing values of $\hbar$. As $\hbar\to 0$ the entanglement entropy, computed at any finite time, converges to a finite nonzero value. The limit law that rules the time dependence of entropy is well reproduced by purely classical computations. Its general features may then be explained by simple classical arguments, which expose the different ways entanglement is generated in systems which are classically chaotic or regular.Comment: 4 pages, 4 figures. New references to published related work have been adde