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quantum-information-theory
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Entanglement Generation and Distribution in Spin Chains
, Ph.D. Dissertation Sharif University of Technology ; Rouhani, Shahin (Supervisor) ; Jafarizadeh, Mohammad Ali (Supervisor)
Abstract
Entanglement is the most important quantity in quantum information processing tasks. However the provision of the required entanglement between various quantum parts is one of the most challenging breakthroughs in realization of quantum processors. One of the scenarios for entangling various parts is use of naturally interacting qubits, called “spin chains”. The low level of required control and the ability of entangling mesoscopicaly separated parts cause such systems to be attractive for using in future low dimensional silicone compatible technology quantum processors. Accordingly in this thesis by considering a ferromagnetic spin system in which is conserved and by initializing the...
Introducing an Upper bound on Capacity of Quantum Key Distillation
, M.Sc. Thesis Sharif University of Technology ; Aref, Mohammad Reza (Supervisor) ; Aminzadeh Gohari, Amin (Supervisor)
Abstract
In modern cryptography the main goal in symmetric cryptography algorithms is that the security of the protocol should be only dependent on the secrecy of key. Further, secret key agreement has a major role in perfect security. However, it is impossible to share a secrete key only by the use of a public channel and there must be another shared source. This source can be for instance random variables with some joint distribution (as in source model classical key distillation problem) or it can be some entangled quantum systems (as in quantum key distillation problem). The question here is that with the optimum efficiency, what is the maximum number of key bits that can be distilled from one...
Perfect State Transfer in Two & Three Dimensional Structures
, M.Sc. Thesis Sharif University of Technology ; Karimipour, Vahid (Supervisor)
Abstract
Since the inception of the fields of quantum information and computation, the task of coherently transferring quantum states, through long and short distances has been of utmost importance. While photons are the ideal carriers of quantum information over long distances, it has become evident that the best possible method for transferring quantum information over short distances, i.e. through regular arrays of qubits, is to exploit the natural dynamics of the many body system. This idea was first introduced in the work of Bose [2] who showed that the natural dynamics of a Heisenberg ferromagnetic chain can achieve high-fidelity transfer of spin states over distances as long as 80 lattice...
Analysis of Entanglement in Ladder Lattices
, M.Sc. Thesis Sharif University of Technology ; Jafari, Akbar (Supervisor) ; Rezakhani, Ali (Supervisor)
Abstract
Since concepts in quantum information theory has recently been applied to characterize states in many-body systems, we survey entanglement of the ground states in the S = 1/2 antiferromagnetic Heisenberg ladder systems and 2D square lattices. The Lancz¨os method for exact diagonalization of quantum spin models are used to find the ground states. Moreover, effect of defect in ladder on entanglement and ground state energy are studied
Design and Optimization of the Operation and Readout of Superconductor Qubits
,
Ph.D. Dissertation
Sharif University of Technology
;
Khorasani, Sina
(Supervisor)
;
Fardmanesh, Mehdi
(Supervisor)
Abstract
Computational instruments such as personal computers (PC) are among the most important and developed inventions needed for the society. Nowadays, the fastest classical computing machines are based on the conventional semiconductor fabrication technology. But these computers cannot satisfy all of the requirements of today’s ongoing developments. Two important weaknesses of the undergoing technology are the speed of computing which is in the frontend of the semiconductor technology, and solving some complicated problems which may take years and even decades with these computers. This is while, based on quantum theory and related algorithms, solving of these problems would take much less time....
An Investigation on Entanglement and Its Applications in Quantum Communication Protocols
, M.Sc. Thesis Sharif University of Technology ; Aref, Mohammad Reza (Supervisor) ; Aminzadeh Gohari, Amin (Co-Advisor)
Abstract
In this thesis, we propose a new method for deriving the achievability results in quantum information theoretic problems. The calssical quan- tum decoupling lemma is an essential component in our method. Assume that each classical source is randomly binned at a finite rate. We find sufficient conditions on these rates such that the bin indices are nearly mutually independent of each other and of a quantum source Qn. Us- ing this theorem in conjunction with the calssical quantum Slepian Wolf (CQSW) result, this method suggest a new comprehensive framework for the achievability of network quantum information theoretic prob- lems. We’ve used the new method to redrive the Holevo bound, private...
Finding Semi-Optimal Measurements for Entanglement Detection Using Autoencoder Neural Networks
, M.Sc. Thesis Sharif University of Technology ; Raeisi, Sadegh (Supervisor)
Abstract
Entanglement is one of the key resources of quantum information science which makes identification of entangled states essential to a wide range of quantum technologies and phenomena.This problem is however both computationally and experimentally challenging.Here we use autoencoder neural networks to find semi-optimal measurements for detection of entangled states. We show that it is possible to find high-performance entanglement detectors with as few as three measurements. Also, with the complete information of the state, we develop a neural network that can identify all two-qubits entangled states almost perfectly.This result paves the way for automatic development of efficient...
Quantum Process Tomography: A New Approach Based on Moments
, M.Sc. Thesis Sharif University of Technology ; Tayefeh Rezakhani, Ali (Supervisor)
Abstract
In this report, we have formulated a new technique for characterizing quantum optical processes based on probing unknown processes only with coherent states and simply by measuring normally-ordered moments of output states. Our method has two substantial advantages in comparison with previous methods.First, for practical purposes of uantum-optical communications and information, predicting of the classicality or nonclassicality of output states from an unknown quantum process is generally important. Because of truncation of the Hilbert space in the Fock basis and/or exploiting Klauder theorem, antecedent methods failed to carry out foretelling the [non]classicality features of the process’...
Investigation of Thermodynamic Relations in Microscopic Systems by Quantum Information Theory
, M.Sc. Thesis Sharif University of Technology ; Shafiee, Afshin (Supervisor) ; Shamkhali, Amir Naser (Supervisor)
Abstract
Entropy is one of the important quantities in thermodynamics. In this project has tried to make this quantity as a bridge between quantum and thermodynamics. Entropy has many definitions that the Shannon entropy is chosen in this work. By this definition of entropy, we are able to define the entropy for a electronic system in molecules. By this definition, we are seeking an answer for this question,”whether entropy has a similar application in quantum like thermodynamics or not?”. To elucidate this hypothesis, simple diatomic molecules are computed. In fact, displacement of the Shannon entropy has investigated in bond making process. The question is that whether we can use this quantity to...
Relation Between Correlation and Energy in Quantum Thermodynamics
, Ph.D. Dissertation Sharif University of Technology ; Rezakhani, Ali (Supervisor) ; Huber, Marcus (Supervisor) ; Jafari, Akbar (Supervisor)
Abstract
Quantum thermodynamics is a new field of study in physics, which by considering the fundamentals of statistical mechanics, open quantum system, quantum information and mesoscopic system aims at the investigation of quantum systems from a thermodynamical point of view. To achieve these aims, a better understanding of the relations between quantum and thermodynamics fundamentals is essential. Energy and correlation are two key concepts in statistical mechanics and quantum thermodynamics (and information), respectively, that studying the relation between them will shed light on the fundamentals of quantum thermodynamics. As generating any correlation in quantum systems with initial heat state...
A Study of Quantum Information Transfer from DNA to Protein
, M.Sc. Thesis Sharif University of Technology ; Shafiee, Afshin (Supervisor)
Abstract
New biological discussions in quantum mechanics that has grown considerably in the past decade. Meanwhile, considering some of interesting problems in biology and chemistry, the use of quantum approach superposition principle and tunneling effect explain some of the phenomena of life more than several. Nowadays, regarding quantum description, provided to explain how we recognize different odors, what the mechanism photosynthesis is, and how bind navigation occurs. Furthermore, the new field of quantum biology sheds light in underestanding the issue of heritance and genetics inforamtion. In this thesis, after reviewing some interesting topics of quantum biology, the data transfer from...
Quantum Information Theory and Holography
, M.Sc. Thesis Sharif University of Technology ; Karimipour, Vahid (Supervisor) ; Naseh, Ali (Co-Supervisor)
Abstract
In this thesis, we investigate some of the quantum information theoretic approaches in gauge-gravity duality and specially AdS/CFT. Our main focus is the entanglement entropy on the boundary of a holographic theory and its dual on bulk which is called Ryu-Takayanagi (RT) surface. We show that a tensor network model of particles, named HaPPY model, can mimic the RT formula. After proving the RT formula in this model, we introduce a new class of multipartite entangled state named Planar Maximally Entangled (PME) states which can be used as an alternative building block in HaPPY model. We classify PME state of four qubits and give some example of these states for general number of particles....
On dimension bounds for auxiliary quantum systems
, Article IEEE Transactions on Information Theory ; Vol. 60, Issue. 1 , Jan , 2014 , PP . 368-387 ; ISSN: 00189448 ; Gohari, A ; Sharif University of Technology
Abstract
Expressions of several capacity regions in quantum information theory involve an optimization over auxiliary quantum registers. Evaluating such expressions requires bounds on the dimension of the Hilbert space of these auxiliary registers, for which no nontrivial technique is known; we lack a quantum analog of the Carathéodory theorem. In this paper, we develop a new non-Carathéodory-type tool for evaluating expressions involving a single quantum auxiliary register and several classical random variables. As we show, such expressions appear in problems of entanglement-assisted Gray-Wyner and entanglement-assisted channel simulation, where the question of whether entanglement helps in these...
Algorithmic proof for the completeness of the two-dimensional Ising model
, Article Physical Review A - Atomic, Molecular, and Optical Physics ; Volume 86, Issue 5 , 2012 ; 10502947 (ISSN) ; Zarei, M. H ; Sharif University of Technology
2012
Abstract
We show that the two-dimensional (12D) Ising model is complete, in the sense that the partition function of any lattice model on any graph is equal to the partition function of the 2D Ising model with complex coupling. The latter model has all its spin-spin coupling equal to iπ4 and all parameters of the original model are contained in the local magnetic fields of the Ising model. This result has already been derived by using techniques from quantum information theory and by exploiting the universality of cluster states. Here we do not use the quantum formalism and hence make the completeness result accessible to a wide audience. Furthermore, our method has the advantage of being algorithmic...
Group-covariant extreme and quasiextreme channels
, Article Physical Review Research ; Volume 4, Issue 3 , 2022 ; 26431564 (ISSN) ; Sanders, B. C ; Sharif University of Technology
American Physical Society
2022
Abstract
Constructing all extreme instances of the set of completely positive trace-preserving (CPTP) maps, i.e., quantum channels, is a challenging and valuable open problem in quantum information theory. Here we introduce a systematic approach that, despite the lack of knowledge about the full parametrization of the set of CPTP maps on arbitrary Hilbert-spaced dimension, enables us to construct exactly those extreme channels that are covariant with respect to a finite discrete group or a compact connected Lie group. Innovative labeling of quantum channels by group representations enables us to identify the subset of group-covariant channels whose elements are group-covariant generalized-extreme...