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Dissipative quantum metrology in manybody systems of identical particles
, Article New Journal of Physics ; Vol. 16, issue , January , 2014 ; Alipour, S ; Rezakhani, A. T ; Sharif University of Technology
Abstract
Estimation of physical parameters is essential in almost any part of science and technology. The enhancement of performance in this task (e.g. beating the standard classical shot-noise limit) using available physical resources is a major goal in metrology. Quantum metrology in closed systems has indicated that entanglement in such systems may be a useful resource. However, whether in open quantum systems such enhancements may still show up is not yet fully understood. Here, we consider a dissipative (open) quantum system of identical particles in which a parameter of the open dynamics itself is to be estimated. We employ a recently developed dissipative quantum metrology framework, and...
Quantum metrology in open systems: Dissipative cramer-rao bound
, Article Physical Review Letters ; Volume 112, Issue 12 , 2014 ; 00319007 (ISSN) ; Mehboudi, M ; Rezakhani, A. T ; Sharif University of Technology
American Physical Society
2014
Abstract
Estimation of parameters is a pivotal task throughout science and technology. The quantum Cramér-Rao bound provides a fundamental limit of precision allowed to be achieved under quantum theory. For closed quantum systems, it has been shown how the estimation precision depends on the underlying dynamics. Here, we propose a general formulation for metrology scenarios in open quantum systems, aiming to relate the precision more directly to properties of the underlying dynamics. This feature may be employed to enhance an estimation precision, e.g., by quantum control techniques. Specifically, we derive a Cramér-Rao bound for a fairly large class of open system dynamics, which is governed by a...
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
Deciphering the electric field changes in the channel of an open quantum system to detect DNA nucleobases
, Article Journal of Computational Electronics ; Volume 16, Issue 2 , 2017 , Pages 411-418 ; 15698025 (ISSN) ; Berahman, M ; Yazdanpanah Goharrizi, A ; Sharif University of Technology
Abstract
DNA nucleobases strongly absorbed onto a graphene sheet placed between two gold electrodes in a contact–channel–contact configuration were distinguished. We analyzed the system using the nonequilibrium Green’s function method combined with density functional theory. The changes of the electric field in the middle of the vacuum gap (channel) were investigated. The Mulliken population was deciphered for graphene and the nucleobases. We also extracted the image plane, which was found to lie very close to the position of peak induced density. The projection of the electron difference density and electrostatic difference potential of the nucleobases are also presented. The nucleobases were...
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...
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...