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Binding Energy of Multi-Partite Quantum Systems based on Quantum Thermodynamics Viewpoint
, Ph.D. Dissertation Sharif University of Technology ; Bahrampour, Alireza (Supervisor) ; Rezakhani, Ali (Supervisor)
Abstract
Examining composite quantum systems through quantum thermodynamics, we face the new concept of binding energy. In this thesis, we are going to present a general definition for binding energy in quantum systems which covers any kind of interactions. First of all, we examine the possibility of energy exchange in a quantum system using quantum thermodynamics. In this theory, energy exchanges of an open quantum system may be divided in to two portions: heat and work; due to an accepted definition, heat is the portion of energy that is supposed to change entropy, while work has no influence on that. In this research, we restrict our calculations to the systems which are thermally closed and...
Quantum Markovian Evolutions in Adiabatic and Nonadiabatic Regimes
, M.Sc. Thesis Sharif University of Technology ; Memarzadeh, Laleh (Supervisor)
Abstract
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...
Efficiency of Excitonic Energy Transfer Phenomenon in Multi-Levels Quantum Systems
, Ph.D. Dissertation Sharif University of Technology ; Rezakhani, Ali (Supervisor)
Abstract
The process of energy transfer in quantum systems is an interesting phenomenon due to the emergence of quantum effects . This phenomena can be studied in one of two possible spaces : real space and energy space of the system . In addition , to evaluate how this process is successful , one can define an efficiency as the population of a target state . Finding the approaches to increase this quantity takes into account one of the main objectives of the current researches . On the other hand , isolating the quantum systems from the surrounding environment (bath) in practice is impossible and then interaction between them is inevitable . In this research , we provide a comprehensive...
Review of the Range of Validity of Markovian Master Equations for Harmonic Oscillators
, M.Sc. Thesis Sharif University of Technology ; Rezakhani, Ali (Supervisor)
Abstract
Quantum mechanics, in the first place, investigates systems by introducing some principals about Hilbert space, Schrodinger equation etc. which are recognized as closed quantum systems. In principal, this is not possible to separate a system from its surrounding environment. Thus, the implications of the environment on the evolution of the system must be taken into consideration. As a matter of fact, all systems are considered open in a sense that, it is interacting with another system called the environment. In such circumstances, we tend to represent a description of open quantum systems in a way that following the evolution of the total system, i.e. system and the environment, is not...
Calculation of Quantum Transition Probabilities between Codons and Concept of Biological Information
, Ph.D. Dissertation Sharif University of Technology ; Shafiee, Afshin (Supervisor)
Abstract
It has been about a century since the introduction of the theory of quantum mechanics. This theory is a branch of physics that describes the behavior of nature in very small scales and microscopic systems . Since no quantum system is entirely isolated from its surroundings , it is necessary to study their interactions with the environment to understand them accurately. The theory of open quantum systems provides the theoretical and conceptual framework needed to consider these interactions. Then using the appropriate quantum operations , the evolution of the combined system can be investigated. Moreover , considering the environmental effects, some quantum features such as dissipation...
Quantum Estimation in Open Systems
, Ph.D. Dissertation Sharif University of Technology ; Karimipour, Vahid (Supervisor)
Abstract
In this thesis, we investigate the problem of quantum estimation in open quantum sys- tems. To this end, after a review of classical and quantum estimation theory, and the role of different properties of the quantum systems in enhancing estimation of the closed systems, we will study different characteristics of the open systems. Non-Markovianity of a dynamics is a quantum property which is a special feature of open systems dynamics. It is expected that this property plays a role in the precession of the estimation. Since there is no universal measure for distinguishing Markovian and non-Markovian dynamics, we first use quantum discord between the system and the environment as a measure for...
Effects of Non-Markovian dynamics on the Energy Transport Processes in a Quantum Network
, M.Sc. Thesis Sharif University of Technology ; Rezakhani, Ali (Supervisor)
Abstract
In this thesis we are going to study the effects of Non-Markovianity on the excitation energy transport(EET) and compare it with Markovian effects. We will see that the shape of a network affects its efficiency. The speed of EET in linear networks is slowed down as Non-Markovianity is increased and this in turn lowers the efficiency of linear networks in Non-Markovian regime. Finally, we compare the efficiency of different networks
Thermodynamical Investigation of Quantum Systems
, Ph.D. Dissertation Sharif University of Technology ; Golshani, Mehdi (Supervisor)
Abstract
Investigation of the consistency between physical theories has always resulted in the advancement of physics. Meanwhile, study of the consistency between quantum mechanics and thermodynamics has led to the development of a branch in theoretical physics called quantum thermodynamics. In addition to the consistency problem,employing other features of quantum mechanics such as coherency and entanglement, to enhance thermodynamic processes is another ongoing subject of research. In order to study the thermodynamics of quantum systems, we use the first law of thermodynamics to present a derivation of quantum potential. Quantum potential is a term in the equations of motion of a quantum system of...
Optimal Coherent Control of Quantum Dynamics: Process-Based Approach
, Ph.D. Dissertation Sharif University of Technology ; Rezakhani, Ali (Supervisor)
Abstract
One of the main tools of the developing quantum technology is making the desired quantum gates and processes in the presence of the environmental noises. In this thesis, we first derive a Markovian master equation which defines purely the time evolution of the dynamics (process matrix) of the open system rather than its state (density matrix). This master equation indeed describes the time evolution of the Choi-Jamiolkowsli matrix which is independent of the state of the system at all times including the initial state. The n, by using this master equation we provide a scheme to manipulate optimally and locally the dynamics of the open system by external coherent agents. Such scheme...
Generation of Quantum Correlation by the Environment
, M.Sc. Thesis Sharif University of Technology ; Memarzadeh, Laleh (Supervisor)
Abstract
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 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...
Critical Investigation of Decoherecne Theory in Different Physical Contexts
, Ph.D. Dissertation Sharif University of Technology ; Shafiee, Afshin (Supervisor)
Abstract
Considering the consistency between the predictions of a theory with what is observed in experience, Quantum Mechanics is the most accurate theory in the history of physics. However, is does not present us an unmbigiuos and realistic description about the nature of the microscopic phenomena. At the heart of these issues is the so-called measurement problem. The formalism of the quantum mechanics is unitary and deterministic. Nevertheles, when one does measurements, the unitary process of the evolution of wave-function breaks due to a stochastic abruption. The results of the measurements are in correspondence with the everyday experience of the observer. Yet, the theory itself does not...
Dynamical Behavior in Statistical Mechanics of Open Quantum Systems
, M.Sc. Thesis Sharif University of Technology ; Rezakhani, Ali (Supervisor)
Abstract
A fundamental question in investigating decoherence and equilibrium of a system in contact with a bath is how its entropy changes in time. Normally, von Neumann’s entropy is used in such studies to quantize degree of decoherence. Recently, certain researches have been conducted addressing entropy rate and various bounds have been achieved for this quantity, utilizing which one can discuss decoherence rate and equilibrium state of open systems.In this thesis, we introduce these bounds and try to improve them. Using improved bound we will show that for almost all conceivable initial states of the system and the bath, average of entropy rate will be negligible. This result is obtained under...
The Role of Quantum Coherence and Geometry on the Excitonic Energy Transfer in Photosynthetic Structures
, M.Sc. Thesis Sharif University of Technology ; Karimipour, Vahid (Supervisor) ; Rezakhani, Ali (Supervisor)
Abstract
It has been of great interest to know whether quantum effects can play an essential role in the biological processes. Considering that quantum features, such as coherence and entanglement,can be harnessed to perform quantum information processing tasks, which are believed to be hard classically, the question is whether nature has also exploited these features in order to enhance the performance of biological systems. Although the presence of warm and wet environment around the biological systems results in the rapid destruction of quantum effects, recent experiments reported the existence of quantum coherence in light-harvesting complexes of some photosynthetic systems.This coherence lasts...
Classicalization of quantum state of detector by amplification process
, Article Physics Letters, Section A: General, Atomic and Solid State Physics ; Volume 383, Issue 15 , 2019 , Pages 1677-1682 ; 03759601 (ISSN) ; Taher Ghahramani, F ; Asadian, A ; Golshani, M ; Sharif University of Technology
Elsevier B.V
2019
Abstract
It has been shown that a macroscopic system being in a high-temperature thermal coherent state can be, in principle, driven into a non-classical state by coupling to a microscopic system. Therefore, thermal coherent states do not truly represent the classical limit of quantum description. Here, we study the classical limit of quantum state of a more relevant macroscopic system, namely the pointer of a detector, after the phase-preserving linear amplification process. In particular, we examine to what extent it is possible to find the corresponding amplified state in a superposition state, by coupling the pointer to a qubit system. We demonstrate quantitatively that the amplification process...
The effect of probe-ohmic environment coupling type and probe information flow on quantum probing of the cutoff frequency
, Article Physics Letters, Section A: General, Atomic and Solid State Physics ; Volume 383, Issue 35 , 2019 ; 03759601 (ISSN) ; Zandi, M. H ; Bahrampour, A ; Sharif University of Technology
Elsevier B.V
2019
Abstract
This work aims to compare results of dissipating and pure dephasing single-qubit probes in characterizing the cutoff frequency of a harmonic reservoir Ohmic spectral density. In particular, we proved that a dissipating single-qubit improves the estimation precision of the cutoff frequency estimator. The information backflow and outflow of the dissipating and the dephasing single-qubit are compared. The relation between the quantum Fisher information and the information outflow and backflow of the probe is obtained. The results show that difference between the values of information outflow and backflow of a dissipating single-qubit is larger than a dephasing single-qubit. So, a single-qubit...
Accessible maps in a group of classical or quantum channels
, Article Open Systems and Information Dynamics ; Volume 29, Issue 1 , 2022 ; 12301612 (ISSN) ; Shahbeigi, F ; Puchała, Z ; Zyczkowski, K ; Sharif University of Technology
World Scientific
2022
Abstract
We study the problem of accessibility in a set of classical and quantum channels admitting a group structure. Group properties of the set of channels, and the structure of the closure of the analyzed group G plays a pivotal role in this regard. The set of all convex combinations of the group elements contains a subset of channels that are accessible by a dynamical semigroup. We demonstrate that accessible channels are determined by probability vectors of weights of a convex combination of the group elements, which depend neither on the dimension of the space on which the channels act, nor on the specific representation of the group. Investigating geometric properties of the set A of...
Quantum detailed balance conditions and fluctuation relations for thermalizing quantum dynamics
, Article Physical Review E ; Volume 98, Issue 5 , 2018 ; 24700045 (ISSN) ; Benatti, F ; Floreanini, R ; Marcantoni, S ; Golshani, M ; Tayefeh Rezakhani, A ; Sharif University of Technology
American Physical Society
2018
Abstract
Quantum detailed balance conditions and quantum fluctuation relations are two important concepts in the dynamics of open quantum systems: both concern how such systems behave when they thermalize because of interaction with an environment. We prove that for thermalizing quantum dynamics the quantum detailed balance conditions yield validity of a quantum fluctuation relation (where only forward-time dynamics is considered). This implies that to have such a quantum fluctuation relation (which in turn enables a precise formulation of the second law of thermodynamics for quantum systems) it suffices to fulfill the quantum detailed balance conditions. We, however, show that the converse is not...
Fluctuation relation for heat exchange in Markovian open quantum systems
, Article Physical Review E ; Volume 97, Issue 4 , April , 2018 ; 24700045 (ISSN) ; Golshani, M ; Tayefeh Rezakhani, A ; Sharif University of Technology
American Physical Society
2018
Abstract
A fluctuation relation for the heat exchange of an open quantum system under a thermalizing Markovian dynamics is derived. We show that the probability that the system absorbs an amount of heat from its bath, at a given time interval, divided by the probability of the reverse process (releasing the same amount of heat to the bath) is given by an exponential factor which depends on the amount of heat and the difference between the temperatures of the system and the bath. Interestingly, this relation is akin to the standard form of the fluctuation relation (for forward-backward dynamics). We also argue that the probability of the violation of the second law of thermodynamics in the form of the...
Minimum output entropy of a non-gaussian quantum channel
, Article Physical Review A - Atomic, Molecular, and Optical Physics ; Volume 94, Issue 2 , 2016 ; 10502947 (ISSN) ; Mancini, S ; Sharif University of Technology
American Physical Society
2016
Abstract
We introduce a model of a non-Gaussian quantum channel that stems from the composition of two physically relevant processes occurring in open quantum systems, namely, amplitude damping and dephasing. For it we find input states approaching zero output entropy while respecting the input energy constraint. These states fully exploit the infinite dimensionality of the Hilbert space. Upon truncation of the latter, the minimum output entropy remains finite, and optimal input states for such a case are conjectured thanks to numerical evidence
Thermal effect and role of entanglement and coherence on excitation transfer in a spin chain
, Article Iranian Journal of Physics Research ; Volume 19, Issue 2 , 2019 , Pages 405-413 ; 16826957 (ISSN) ; Sharif University of Technology
Isfahan University of Technology
2019
Abstract
We analyze the role of bath temperature, coherence and entanglement on excitation transfer in a spin chain induced by the environment. In Markovian regime, we show that coherence and entanglement are very sensitive to bath temperature and vanish in time in contrary to the case of having zero-temperature bath. That is while, finding the last qubit of the chain in excited state increases by increasing the bath temperature. The obtained results show the destructive role of temperature on coherence and entanglement and confirm that these quantum mechanical features cannot affect probability of finding the last qubit in excited state. © 2019, Isfahan University of Technology. All rights reserved