Environmental effects on quantum geometric phase and quantum entanglement

Download

index.pdf

Date

2008

Author

Günhan, Ali Can

Metadata

Show full item record

Item Usage Stats

171
views

67
downloads

We investigate the geometric phase (GP) acquired by the states of a spin-1/2 nucleus which is subject to a static magnetic field. This nucleus as the carrier system of GP, is taken as coupled to a dissipative environment, so that it evolves non-unitarily. We study the effects of different characteristics of different environments on GP as nucleus evolves in time. We showed that magnetic field strength is the primary physical parameter that determines the stability of GP; its stability decreases as the magnetic field strength increases. (By decrease in stability what we mean is the increase in the time rate of change of GP.) We showed that this decrease can be very rapid, and so it could be impossible to make use of it as a quantum logic gate in quantum information theory (QIT). To see if these behaviors differ in different environments, we analyze the same system for a fixed temperature environment which is under the influence of an electromagnetic field in a squeezed state. We find that the general dependence of GP on magnetic field does not change, but this time the effects are smoother. Namely, increase in magnetic field decreases the stability of GP also for in this environment; but this decrease is slower in comparison with the former case, and furthermore it occurs gradually. As a second problem we examine the entanglement of two atoms, which can be used as a two-qubit system in QIT. The entanglement is induced by an external quantum system. Both two-level atoms are coupled to a third two-level system by dipole-dipole interaction. The two atoms are assumed to be in ordinary vacuum and the third system is taken as influenced by a certain environment. We examined different types of environments. We show that the steady-state bipartite entanglement can be achieved in case the environment is a strongly fluctuating, that is a squeezed-vacuum, while it is not possible for a thermalized environment.

Subject Keywords

Physics., Quantum computers.

URI

http://etd.lib.metu.edu.tr/upload/3/12609450/index.pdf
https://hdl.handle.net/11511/17987

Collections

Graduate School of Natural and Applied Sciences, Thesis

Suggestions

OpenMETU
Core

Nonlinear optical properties of semiconductor heterostructures Yıldırım, Hasan; Tomak, Mehmet; Department of Physics (2006) The nonlinear optical properties of semiconductor heterostructures, such as GaAsAl/GaAs alloys, are studied with analytic and numerical methods on the basis of quantum mechanics. Particularly, second and third-order nonlinear optical properties of quantum wells described by the various types of confining potentials are considered within the density matrix formalism. We consider a Pöschl-Teller type potential which has been rarely considered in this area. It has a tunable asymmetry parameter, making it a goo...
Entanglement transformations and quantum error correction Gül, Yusuf; Pak, Namık Kemal; Department of Physics (2009) The main subject of this thesis is the investigation of the transformations of pure multipartite entangled states having Schmidt rank 2 by using only local operations assisted with classical communications (LOCC). A new parameterization is used for describing the entangled state of p particles distributed to p distant, spatially separated persons. Product, bipartite and truly multipartite states are identified in this new parametrization. Moreover, alternative parameterizations of local operations carried o...
Quantum systems and representation theorem Dosi, Anar (2013-09-01) In this paper we investigate quantum systems which are locally convex versions of abstract operator systems. Our approach is based on the duality theory for unital quantum cones. We prove the unital bipolar theorem and provide a representation theorem for a quantum system being represented as a quantum -system.
Gravitational waves and gravitational memory Korkmaz, Ali; Tekin, Bayram; Department of Physics (2018) We study the gravitational waves produced by compact binary systems in the linear regime of massless general relativity and calculate the gravitational memory produced by these waves on a detector.
Energy spectrum of a 2D Dirac oscillator in the presence of a constant magnetic field and an antidot potential Akçay, Hüseyin; Sever, Ramazan (2016-07-04) We investigate the energy spectrum and the corresponding eigenfunctions of a 2D Dirac oscillator confined by an antidot potential in the presence of a magnetic field and Aharonov-Bohm flux field. Analytical solutions are obtained and compared with the results of the Schrodinger equation found in the literature. Further, the dependence of the spectrum on the magnetic quantum number and on the repulsive potential is discussed.

Citation Formats

A. C. Günhan, “Environmental effects on quantum geometric phase and quantum entanglement,” Ph.D. - Doctoral Program, Middle East Technical University, 2008.