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quantum-entanglement
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Entanglement and State Transfer through Quantum Spin Chains
, M.Sc. Thesis Sharif University of Technology ; Memarzadeh, Laleh (Supervisor) ; Langari, Abdollah (Supervisor)
Abstract
In this thesis, we will examine quantum state and entanglement transfer. Quantum state and entanglement transfer are requirements for the development of quantum technology. Transferring the output state of a quantum processor to the next processor, which can be at an arbitrary distance from the first processor, is one of the direct applications of quantum state transfer. On the other hand, entanglement transmission is a necessary prerequisite for quantum protocols. For example, preparing the entangled pair in a laboratory and transferring one share of an entangled pair to another place in order to create entanglement between different points is essential for building quantum networks. Also,...
Quantum Information Processing with NMR Spectroscopy
, M.Sc. Thesis Sharif University of Technology ; Raeisi, Sadegh (Supervisor)
Abstract
Quantum Information Processing (QIP) is one of the active areas of research in both theoretical and experimental physics. Any experimental technique that is used for a scalable implementation of QIP must satisfy DiVincenzo’s criteria [17]. Nuclear Magnetic Resonance (NMR) satisfies many of these conditions, but it is not scalable and cannot initialize the qubits to pure state [28]. NMR can be a great platform for studying the fundamentals of QIP. In this project, for a twoqubit system, we prepare pseudo pure states from the initial mixed states by using unitary operations and implement CNOT gates. According to the results of our experiments, we can apply all the gates with high fidelity....
Investigation of Quantum States of Light (Generation and Utilization Their Special Properties) in Quantum Information Science and Precision Measurements
, M.Sc. Thesis Sharif University of Technology ; Karimipour, Vahid (Supervisor)
Abstract
Quantum entanglement and superposition are wonderful and mysterious phenomena of quantum mechanics. By means of quantum entanglement, two or more systems become partner in state of each other . As a result, measurements on each of these systems affect the status of other systems. Quantum superposition allows a system inhabits several of its possible quantum states simultaneously. These two features are applicable in many technologies in present age. Photons, as an quantum unit of light, are appropriate candidate for utilization these properties. Because they are robust to decoherence and for their preparation exist various methods. Hence, we interested to generation of quantum states of...
Entanglemant: Standard QM nersus Bohmian QM
, M.Sc. Thesis Sharif University of Technology ; Golshani, Mehdi (Supervisor)
Abstract
The1935 EPR thought experiment, introduced the concept of entanglement of quantum states, and this brought up the problems of faster than light signaling and faster than light influencing.The quantum entanglement has becomeone of the most important aspects of quantum information in the last thirty years.But the standard quantum theory has not been able to solve the dilemma of quantum entanglement and has confined itselfto deny faster than light signaling, but admitting faster than light influencing.But the followers of Bohmian mechanics,which have appealed to hidden variables,see no problem with quantum entanglement.The aim of this thesis is to compare the status of the standard quantum...
Aspects of Entanglement in Quantum Field Theory and Quantum Gravity, using the Holography
, Ph.D. Dissertation Sharif University of Technology ; Arfaei, Hessamaddin (Supervisor) ; Mosaffa, Amir Esmaeil (Supervisor) ; Alishahiha, Mohsen (Co-Advisor)
Abstract
Entanglement is an immediate consequence of quantum mechanical pos- tulates and is thus an indispensable part of studying quantum systems. A very useful quantity which can appropriately quantify entanglement between the degrees of freedom of a composite quantum system is En- tanglement Entropy (EE).
Over the last few years, this subject has attracted a lot of interest both in QFT and in the context of holography. On the one hand, an intu- itive geometrical Holographic model for entanglement entropy has been proposed in the context of gauge/gravity duality, and on the other, var- ious issues concerning entanglement have been explored, e.g. in quan- tum computation, quantum information...
Over the last few years, this subject has attracted a lot of interest both in QFT and in the context of holography. On the one hand, an intu- itive geometrical Holographic model for entanglement entropy has been proposed in the context of gauge/gravity duality, and on the other, var- ious issues concerning entanglement have been explored, e.g. in quan- tum computation, quantum information...
Superluminal Signaling in the Relationship Between Quantum Mechanics and Special Relativity
, M.Sc. Thesis Sharif University of Technology ; Golshani, Mehdi (Supervisor)
Abstract
Non-locality was taken into account, in the first place by Bell’s inequalities in Quantum Mechanics. With the emergence of non-locality, it seems that there is a fundamental conflict between the two basic theories of the 20th century, Quantum Mechanics and Relativity. Relativity is constructed upon local descriptions, but there are some hidden non-local features in Quantum Mechanics .Thus, superluminal signaling, which is in conflict with Relativity, has attracted a lot of attention and some ideas were proposed , using this non-local feature, to send superluminal signal. But, the no-signaling theorems claim that none of these features can be used to send superluminal signal. On the other...
Constructing and Study of 1d And Quasi-1d Spin Models Through Matrix Product States Formalism (Mps)
, Ph.D. Dissertation Sharif University of Technology ; Karimipour, Vahid (Supervisor)
Abstract
Matrix Product States (MPS) is an analytical formalism to construct solvable many-body quan-tum models, which is based on the concepts of quantum information and computation theory. In this dissertation, We briefly review the history of matrix product states. We follow these states from quantum Markovian states(QMS) and valence bond solid states(VBS) to finitely correlated states(FCS) and matrix product states(MPS). We then present our method of study-ing and working with MP states and we introduce and study in detail the 1D and quasi-1D solvable spin models that we have been able to successfully construct in this frame work and calculate the corresponding correlations and quantities. These...
Entanglement from dissipative dynamics into overlapping environments
, Article Physical Review A - Atomic, Molecular, and Optical Physics ; Vol. 90, issue. 6 , Dec , 2014 ; Memarzadeh, L ; Mancini, S ; Sharif University of Technology
Abstract
We consider two ensembles of qubits dissipating into two overlapping environments, that is, with a certain number of qubits in common that dissipate into both environments. We then study the dynamics of bipartite entanglement between the two ensembles by excluding the common qubits. To get analytical solutions for an arbitrary number of qubits we consider initial states with a single excitation and show that the largest amount of entanglement can be created when excitations are initially located among side (noncommon) qubits. Moreover, the stationary entanglement exhibits a monotonic (nonmonotonic) scaling versus the number of common (side) qubits
Quantum achievability proof via collision relative entropy
, Article IEEE Transactions on Information Theory ; Vol. 60, issue. 12 , 2014 , pp. 7980-7986 ; ISSN: 00189448 ; Gohari, A
Abstract
In this paper, we provide a simple framework for deriving one-shot achievable bounds for some problems in quantum information theory. Our framework is based on the joint convexity of the exponential of the collision relative entropy and is a (partial) quantum generalization of the technique of Yassaee et al. from classical information theory. Based on this framework, we derive one-shot achievable bounds for the problems of communication over classical-quantum channels, quantum hypothesis testing, and classical data compression with quantum side information. We argue that our one-shot achievable bounds are strong enough to give the asymptotic achievable rates of these problems even up to the...
Uncontrolled disorder effects in fabricating photonic quantum simulators on a kagome geometry: A projected-entangled-pair-state versus exact- diagonalization analysis
, Article Physical Review A - Atomic, Molecular, and Optical Physics ; Vol. 89, Issue. 6 , 2014 ; ISSN: 10502947 ; Dezfouli, B. G ; Ghasemipour, F ; Rezakhani, A. T ; Saberi, H ; Sharif University of Technology
Abstract
We propose a flexible numerical framework for extracting the energy spectra and photon transfer dynamics of a unit kagome cell with disordered cavity-cavity couplings under realistic experimental conditions. A projected-entangled pair state (PEPS) Ansatz to the many-photon wave function allows us to gain a detailed understanding of the effects of undesirable disorder in fabricating well-controlled and scalable photonic quantum simulators. The correlation functions associated with the propagation of two-photon excitations reveal intriguing interference patterns peculiar to the kagome geometry and promise at the same time a highly tunable quantum interferometry device with a signature for the...
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...
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...
Distillation of free entanglement from bound entangled states using weak measurements
, Article Physical Review A - Atomic, Molecular, and Optical Physics ; Volume 88, Issue 6 , 2013 ; ISSN: 10502947 ; Rezakhani, A. T ; Sharif University of Technology
2013
Abstract
We propose a scheme for distillation of free bipartite entanglement from bipartite bound entangled states. The crucial element of our scheme is an ancillary system that is coupled to the initial bound entangled state via appropriate weak measurements. We show that in this protocol free entanglement can be always generated with nonzero probability by using a single copy of the bound entangled state. We also derive a lower bound on the entanglement cost of the protocol and conclude that, on average, applying weaker measurements results in relatively higher values of free entanglement as well as lower costs
Obstacles on the Way Toward an Entropic Uncertainty Relation
, Article International Journal of Theoretical Physics ; 2013 , Pages 1-10 ; 00207748 (ISSN) ; Shafiee, A ; Sharif University of Technology
2013
Abstract
Deutsch's entropic uncertainty relation is examined by using two experiments in which the spin of a single spin-half particle is detected after passing through two Stern-Gerlach apparatuses in two successive times. Two experiments differ only in the angle settings of the Stern-Gerlach apparatuses. In the general case where the angles are arbitrarily arranged, Deutsch's inequality is violated
Creating and detecting micro-macro photon-number entanglement by amplifying and deamplifying a single-photon entangled state
, Article Physical Review Letters ; Volume 110, Issue 17 , April , 2013 ; 00319007 (ISSN) ; Lvovsky, A ; Simon, C ; Sharif University of Technology
2013
Abstract
We propose a scheme for the observation of micro-macro entanglement in photon number based on amplifying and deamplifying a single-photon entangled state in combination with homodyne quantum state tomography. The created micro-macro entangled state, which exists between the amplification and deamplification steps, is a superposition of two components with mean photon numbers that differ by approximately a factor of three. We show that for reasonable values of photon loss it should be possible to detect micro-macro photon-number entanglement where the macrosystem has a mean number of one hundred photons or more
Entanglement dynamics for qubits dissipating into a common environment
, Article Physical Review A - Atomic, Molecular, and Optical Physics ; Volume 87, Issue 3 , 2013 ; 10502947 (ISSN) ; Mancini, S ; Sharif University of Technology
2013
Abstract
We provide an analytical investigation of the entanglement dynamics for a system composed of an arbitrary number of qubits dissipating into a common environment. Specifically, we consider product initial states with a given number of excitations whose evolution remains confined on low-dimensional subspaces of the operators space. We then find for which pairs of qubits entanglement can be generated and can persist at a steady state. Finally, we determine the stationary distribution of entanglement as well as its scaling versus the total number of qubits in the system
Entanglement swapping with local certification: Application to remote micromechanical resonators
, Article 2013 Conference on Lasers and Electro-Optics Europe and International Quantum Electronics Conference, CLEO/Europe-IQEC ; 2013 ; 978-1-4799-0593-5 (ISBN) ; Pirandola, S ; Tombesi, P ; Vitali, D ; Sharif University of Technology
Abstract
Entanglement swapping allows to entangle two distant systems which never interacted. The standard protocol considers two distant users, Alice and Bob, each possessing a bipartite entangled system, R1B1 for Alice and R2B2 for Bob. The users send their systems B1 and B2 to an intermediate station (Charlie). Here an appropriate Bell measurement is made over the B systems and the outcome communicated back to Alice and Bob. As a result, the two remote systems R 1 and R2 become entangled. A delicate point is the experimental verification of the generated entanglement, which generally involves direct measurements on the two remote systems, R1 and R 2, followed by classical communications. A simple...
Quantum optomechanics of a multimode system coupled via a photothermal and a radiation pressure force
, Article Physical Review A - Atomic, Molecular, and Optical Physics ; Volume 86, Issue 4 , 2012 ; 10502947 (ISSN) ; Bahrampour, A. R ; Vitali, D ; Sharif University of Technology
APS
2012
Abstract
We provide a full quantum description of the optomechanical system formed by a Fabry-Pérot cavity with a movable micromechanical mirror whose center-of-mass and internal elastic modes are coupled to the driven cavity mode by both radiation pressure and photothermal force. Adopting a quantum Langevin description, we investigate simultaneous cooling of the micromirror elastic and center-of-mass modes, and also the entanglement properties of the optomechanical multipartite system in its steady state
Crosstalk suppression and high-fidelity measurement in 2-D tunneling of coupled Josephson junctions
, Article IEEE Transactions on Applied Superconductivity ; Volume 22, Issue 4 , 2012 ; 10518223 (ISSN) ; Zandi, H ; Khorasani, S ; Sharif University of Technology
2012
Abstract
We present a new configuration concept in which two similar Josephson junctions are coupled through a capacitor placed in parallel to a dc-superconducting quantum interference device (SQUID) to improve the characteristics of phase qubits. In real coupled quantum systems, because of mutual effects such as crosstalk, entangled quantum states cannot be independently measured. The proposed two-qubit system is demonstrated to have a negligible crosstalk, obtained from the application of a single measurement pulse and an appropriate external flux to one of the junctions and the dc-SQUID, respectively. Surprisingly, the theoretically predicted fidelity for a single-qubit design increases to 99.99%...
Removing correlations in signals transmitted over a quantum memory channel
, Article Physical Review A - Atomic, Molecular, and Optical Physics ; Volume 85, Issue 1 , January , 2012 ; 10502947 (ISSN) ; Memarzadeh, L ; Mancini, S ; Sharif University of Technology
2012
Abstract
We consider a model of a bosonic memory channel, which induces correlations among the transmitted signals. The application of suitable unitary transformations at the encoding and decoding stages allows the complete removal of correlations, thereby mapping the memory channel into a memoryless one. However, such transformations, being global over an arbitrarily large number of bosonic modes, are not realistically implementable. We then introduce a family of efficiently realizable transformations, which can be used to partially remove correlations among errors, and we quantify the reduction of the gap with memoryless channels