Sharif Digital Repository

In this work, the effect of Active Screen Plasma Nitriding (ASPN) treatment on structural, mechanical, electrical and magnetic properties of nanocrystalline Finemet-type alloys with the composition of Fe73.5Si13.5B9Nb3Cu1 and Fe77Si11B9Nb2.4Cu0.6 was investigated. The samples were prepared by vacuum arc melting of high purity constitution in order to obtain a nanocrystalline structure. The rapidly solidified samples on a chilling wheel, were subjected to the ASPN treatment in different temperatures ranging from 410 °C to 560 °C for 3 h and in two gas mixtures of 75% N2-25% H2 and 25% N2-75% H2 at 5 mbar atmosphere. The amorphous ribbons were then annealed under vacuum with the same... 

Entanglement is a type of quantum correlation that plays a crucial role at the heart of almost every quantum algorithm which has led them to outperform their classical counterparts. Recently, a new type of correlation has been introduced. Namely, ”Quantum Discord”. Which is different from the entanglement in the essence, nonetheless it has caused some quantum algorithms to outperform their classical counterparts. Since, creating and maintaining this states is easier than entangled states, they have draw many interests. In this thesis, we review and investigate the use of ”Quantum Discord” for transferring quantum information, in particular remote preparation of quantum states and Remote... 

In most of quantum information protocols, entanglement or, in general expression, quantum correlation, plays the major role. So it is very important to know the ways of generating entanglement and protecting it against noise.
In a general view, environment is usually known as a destructive agent for entangled states. Being exposed to environment, non-diagonal elements of an entangled state’s density matrix would tend to zero, because of decoherence effect. Thus, the entanglement would be disappear. But, recent studies have shown that, this destructive agent can be convert to a useful agent for generating entanglement between system components.
In this thesis, at first, the... 

In this thesis, our aim is to analyse the environment effects on adiabatic and non-adiabatic evolutions. In this regard, first we need to establish a suitable framework for describing the dynamics. While describing the evolution of a quantum system without interaction with its surrounding environment is easy, describing the time evolution of a quantum system in interaction with its surrounding environment is challenging. In this thesis, first we review the formalism for deriving the Markovian master equation for describing the evolution of a system in weak coupling limit. In the standard formalism, it is assumed that the system Hamiltonian is time-independent. But as our aim is to analyse... 

Climate change impacts especially on temperature and precipitation, may have various effects on agriculture and water demand of agriculture sector in different regions around the world. Based on numerous researches, these effects may be positive in a region while another region might endure negative effects. Therefore carrying out researches and developing methods to predict these impacts as well as mitigating strategies seem to be essential. The most worldwide accepted method is using global circulation models (GCMs) outputs under different greenhouse gases emission scenarios, and according to Intergovernmental Panel on Climate Change (IPCC) assessments. IPCC claims that the most recent... 

One of the critical subjects in quantum information science is the transmission of quantum information. Like classical channels, the question of the capacity of quantum channels arises in the quantum information theory; however, in the case of quantum information theory, there are various notions of capacities that can be defined. In quantum channels, information is encoded into the quantum degrees of freedoms, and the channels are used for the transmission of classical and quantum information. Therefore, the classical capacity and quantum capacity of quantum channels are defined as the optimal rate of the transmission of classical and quantum information through quantum channels,... 

Entanglement is one of the unique phenomena in quantum systems that does not have any similar phenomena in classical systems. Entanglement has been used in many protocols of quantum information theory, and there is agreement on its key role in quantum computations and quantum communication protocols. Therefore, studying its dynamics as well as preventing its degradation is important for us. Extensive studies have been done in this field, including the study of entanglement evolution in a situation where all parts of the system are entangled with one of its sub-system has irreversible dynamics due to interaction with its environment [1], [2], [3], [4], [5], [6], [7], [8]. However, the study... 

Currently, quantum noise stands as one of the foremost challenges in the realization of quantum algorithms and the development of quantum technologies. Consequently, finding methods to eliminate or reduce the impact of noise is imperative. This thesis explores the possibility of correcting the expectation values of observables on a quantum system, specifically a qubit quantum system experiences quantum noise, given partial knowledge of the noise. We begin by reviewing essential background information, including some of the most common methods for correcting noise, with a particular focus on the noise deconvolution technique. Subsequently, we introduce our method for correcting the...