Sharif Digital Repository

One of the attractive fields of applied quantum mechanics in recent two-three decades is the field of quantum computing. Up to now different substrates have been proposed for a quantum computer. One of them is cavity quantum electrodynamics in which some quantum systems with finite energy states like atoms interact with quantized Bosonic modes like photons inside a cavity. In this dissertation we study a particular structure in this substrate. This structure consists of some quantum dots inside coupled cavities. Since we would like to build these cavities in a photonic crystal slab, we first introduce two new methods for analysis of this type of crystals. These methods are much faster than... 

Due to climate change and the increase in the emission of greenhouse gasses, the temperature of the large cities is increasing. Tehran, which is the capital of Iran and the most populated city of it, is no exception. One of the significant tools for characterizing heat in the cities is having access to the temperature field of the region. Different tools can be used for achieving the temperature field. Two methods for doing so are remote sensing and numerical models. Each one of the mentioned methods has their own strength and weaknesses. In this research, the WRF-ARW model (version 3.7) is used for deriving meteorological fields for the city of Tehran. One of the many merits of using... 

Nowadays, the significance of securing data and information is undeniable. Cryptography is being used to provide data security. In addition, cryptanalysis is required to evaluate the effectiveness of cryptography methods, and hence, it is an essential concept for securing data. In general, the cryptography functions shall be designed in a way to impose a high load of time-intensive operations to prevent an adversary from accessing the main data from the encrypted data. As a result, cryptography and cryptanalysis algorithms need high performance computations. So far, a number of methods have been proposed to support the required performance. These methods include: distributed computing and... 

Security is an important issue in Vehicular Ad Hoc Networks (VANETs),which are mainly aimed at enhancing safety. Analysis of security mechanisms can help design and implement secure communication establishment methods in such networks. Formal verification is an analysis approach, with the purpose of proving the correctness of a system based on defined precise assumptions. Formal verification is applicable to a vast range of systems, such as time-critical reactive systems. Timed formal verification of cryptographic protocols is a subject that has gained a lot of attention in the recent two decades. The TESLA broadcast authentication protocol is on one hand an efficient, standardized method... 

There is a plethora of research and implementations that intend to increase the performance and reduce implementation costs of network routers. In this work, we review previous designs and propose a new network router design that is based on software-defined networks. Our design separates the data plane and the control plane from each other and connects both parts by using OpenFlow protocol. The control plane consists of a general small computer that utilizes the Quagga software to enforce the routing protocols. The control plane translates routing decisions to OpenFlow instructions and sends them to the data plane. The data plane is based on a switch that supports the OpenFlow protocol... 

Recently, security of integrated circuits has received more attention as ICs have become more complex and their usage has increased in safety critical systems. Many orgeniaztions use the ICs that made by third party companies. This is due to the high costs to build and maintain state-of-the-art semiconductor factories. This subject puts the trustworthiness of the ICs under the question. The chips might be maliciously modified in each stage of the manufacturing chain. This threat is called hardware backdoor in scientific community. The aim of this project is to assess the features embedded in a microprocessor and evaluate the side channel effect of various hardware backdoors. hardware... 

First, we peruse the intraction between a quantized light and a two level atom which has been described by Janes-Cummings-Paul Hamiltonian. By solving Heisenberg equations in Fourier space and describing electric field by a generalized-transverse Green function, we obtain spectral density for a quantum dot which is in the strong coupling to a slab photonic crystal cavity. Afterward, by solving Shrouding equations precisely we demonstrate when quantum dot is in a very strong coupling to cavity, rotate wave approximation is not reliable anymore. It means that if coupling constant gets comparable to cavity mode frequency then the prevalent approach to solve this Hamiltonian will not be correct.... 

In this project, we were intended to study the ultra-strong coupling in optical waveguides. Hence, we analyze the interaction of an electromagnetic wave with a quantum well embedded in a dielectric slab waveguide. First, we designed a QW with and alloys, which the energy of its electron-heavy holes transition is . By exploiting the envelope function approximation, we derived the wavefunction of electrons and holes, their eigen-energies, and the dipole moment of electon-holes. For finding the wavefunction of holes and their eigen-energies, we used the Luttinger Hamiltonian. Next, we calculated the electrical susceptibility of a three level quantum system (as a model for QW), by using... 

Cavity Quantum Electro-Dynamics (CQED) in Weak, Strong and Ultra-Strong coupling Regimes are studied. A MATLAB m-file is written which is able to solve any arbitrary CQED configuration. This program demands input data such as number of Quantum Dots, number of energy levels of each Quantum Dot, energies of each energy level of Quantum Dots, Number of cavity modes, eign-frequency of each cavity mode, coupling constant, dipole strength of each allowed transition of Quantum Dots and initial state of system from user and begins to solve the Schrodinger equation for annihilation and atomic ladder operators. In addition, coefficients of each possible ket will be calculated. Since, any approximation... 

Thin Walled Beams are widely used in engineering applications with the minimum weight design criteria, ranging from civil to aerospace and many other industrial fields. The weight reduction of the beam leads to importance of the dynamic behavior of the structure. Frequently used thin walled beams have low torsional stiffness and their torsional deformations may be of such magnitudes that it is not adequate to treat the angles of cross section rotation as small. When the vibration amplitudes are moderate or large, the geometric nonlinearity must be included and some new phenomena which do not exist in linear torsional dynamic come into play. Unfortunately, the equations of motion of nonlinear... 

In the recent years, photonic crystal (PhC) devices vastly have been paid attention due to their ignorable loss, very low group velocity, flexibility in shape and dimension.In this thesis a PhC coupled cavity ring known as superresonator is introduced and its properties and applications is studied. Also modes of the structure are extracted through both coupled-resonator model and FDTD method, and two of its application is described and studied. Add-drop filter is one of the essential devices in WDM systems. First, an application of superresonator in designing add-drop filters is explained and a novel filter based on the superresonator is introduced and analyzed by FDTD and coupled mode...