649 research outputs found
Diverse applications of the Quantum Walk model in Quantum Information: a theoretical and experimental analysis in the optical framework
Quantum Walks have been a very important model in the last thirty years, after their first definition and rigorous description. The analysis of the many possible variations of their behavior has delivered a plethora of solutions and platforms for the many diverse fields of investigation. The applications of the Quantum Walk model spreads from the development of Quantum Algorithm, to the modeling and simulation of systems of the most diverse nature, such as solid state or biological systems. In general, it helped developing a well-established quantum (or coherent) propagation model, which is useful both inside and outside physics. In this thesis, we focus on the study of disordered Quantum Walks, in order to get better understanding of the inuence of Quantum Walk disordered dynamics to non-classical correlations and propagating quantum information. Afterwards, we generalize this dynamical approach to Quantum Information processing, developing a Quantum Receiver for Quantum State Discrimination featuring a time multiplexing structure and we investigate the potentiality of this Quantum Walk inspired framework in the field of Quantum State Discrimination, through
the developing and realization of experimental protocols characterized by increasing complexity. We also report on some apparent deviations from this path, although still aimed at the transfer of our expertise, built in previous investigations, to the study of new models and more complex quantum systems
The physics of dipolar bosonic quantum gases
This article reviews the recent theoretical and experimental advances in the
study of ultracold gases made of bosonic particles interacting via the
long-range, anisotropic dipole-dipole interaction, in addition to the
short-range and isotropic contact interaction usually at work in ultracold
gases. The specific properties emerging from the dipolar interaction are
emphasized, from the mean-field regime valid for dilute Bose-Einstein
condensates, to the strongly correlated regimes reached for dipolar bosons in
optical lattices.Comment: Review article, 71 pages, 35 figures, 350 references. Submitted to
Reports on Progress in Physic
The effects of Landau level mixing, finite thickness, and external electric fields on the fractional quantum Hall effect
The fractional quantum Hall effect (FQHE) is a unique and interesting experimental and theoretical state. A great deal of experimental, theoretical and numerical work suggests that this state may support quasihole excitations with non-Abelian statistics, where the order of particle exchange influences the final state of the system. Thus, the FQHE offers a system in which the properties of the particles may be explored experimentally and theoretically. Additionally, by controlling the exchange of such particles, it is possible to create a topologically-protected quantum computer. In order to make this possible, however, we must first understand the nature of the ground state. The two leading candidates, the Moore-Read Pfaffian and the anti-Pfaffian, both support non-Abelian excitations, but there has not been a clear answer for which state is realized in experiment. In the present work, we present results of exact diagaonlization calculations which strive to answer this question using a disk geometry. What we find is that the ground state of the system is dependent upon device specific quantities and thus we may be able to engineer samples which will have specific ground state properties
Coherent and dissipative dynamics at quantum phase transitions
The many-body physics at quantum phase transitions shows a subtle interplay
between quantum and thermal fluctuations, emerging in the low-temperature
limit. In this review, we first give a pedagogical introduction to the
equilibrium behavior of systems in that context, whose scaling framework is
essentially developed by exploiting the quantum-to-classical mapping and the
renormalization-group theory of critical phenomena at continuous phase
transitions. Then we specialize to protocols entailing the out-of-equilibrium
quantum dynamics, such as instantaneous quenches and slow passages across
quantum transitions. These are mostly discussed within dynamic scaling
frameworks, obtained by appropriately extending the equilibrium scaling laws.
We review phenomena at first-order quantum transitions as well, whose peculiar
scaling behaviors are characterized by an extreme sensitivity to the boundary
conditions, giving rise to exponentials or power laws for the same bulk system.
In the last part, we cover aspects related to the effects of dissipative
interactions with an environment, through suitable generalizations of the
dynamic scaling at quantum transitions. The presentation is limited to issues
related to, and controlled by, the quantum transition developed by closed
many-body systems, treating the dissipation as a perturbation of the critical
regimes, as for the temperature at the zero-temperature quantum transition. We
focus on the physical conditions giving rise to a nontrivial interplay between
critical modes and various dissipative mechanisms, generally realized when the
involved mechanism excites only the low-energy modes of the quantum
transitions.Comment: Review paper, 138 pages. Final version to appear in Physics Report
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