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Wyniki wyszukiwania dla: quantum decoherence
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Quantum security and theory of decoherence
PublikacjaWe sketch a relation between two crucial, yet independent, fields in quantum information research, viz. quantum decoherence and quantum cryptography. We investigate here how the standard cryptographic assumption of shielded laboratory, stating that data generated by a secure quantum device remain private unless explicitly published, is disturbed by the einselection mechanism of quantum Darwinism explaining the measurement process...
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Quantum Coherence as a Resource
PublikacjaThe coherent superposition of states, in combination with the quantization of observables, represents one of the most fundamental features that mark the departure of quantum mechanics from the classical realm. Quantum coherence in many-body systems embodies the essence of entanglement and is an essential ingredient for a plethora of physical phenomena in quantum optics, quantum information, solid state physics, and nanoscale thermodynamics....
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Decoherence-free communication over multiaccess quantum channels
PublikacjaIn this paper we consider decoherence-free communication over multiple access and k-user quantum channels. First, we concentrate on a hermitian unitary noise model U for a two-access bi-unitary channel and show that in this case a decoherence-free code exists if the space of Schmidt matrices of an eigensubspace of U exhibits certain properties of decomposability. Then, we show that our technique is also applicable for generic random unitary...
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Structure of the Resource Theory of Quantum Coherence
PublikacjaQuantum coherence is an essential feature of quantum mechanics which is responsible for the departure between the classical and quantum world. The recently established resource theory of quantum coherence studies possible quantum technological applications of quantum coherence, and limitations that arise if one is lacking the ability to establish superpositions. An important open problem in this context is a simple characterization...
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Reexamination of the decoherence of spin registers
PublikacjaWe revisit the decoherence process of a multiqubit register interacting with a thermal bosonic bath. We generalize the previous studies by considering not only the register’s behavior but also a part of its environment. In particular, we are interested in information flow from the register to the environment, which we describe using recently introduced multipartite quantum state structures called spectrum broadcast structures....
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Quantum Matter
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Quantum Topology
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QUANTUM ELECTRONICS
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PRX Quantum
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Quantum Reports
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Anomalous decay of quantum correlations of quantum-dot qubits
PublikacjaWe study the evolution of quantum correlations, quantified by the geometric discord, of two excitonic quantum-dot qubits under the influence of the phonon environment. We show that the decay of these correlations differs substantially from the decay of entanglement. Instead of displaying sudden-death-type behavior, the geometric discord shows a tendency to undergo transitions between different types of decay, is sensitive to nonlocal...
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Blurred quantum Darwinism across quantum reference frames
PublikacjaQuantum Darwinism describes objectivity of quantum systems via their correlations with their environment--information that hypothetical observers can recover by measuring the environments. However, observations are done with respect to a frame of reference. Here, we take the formalism of [Giacomini, Castro-Ruiz, & Brukner. Nat Commun 10, 494 (2019)], and consider the repercussions on objectivity when changing quantum reference...
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Quantum entanglement
PublikacjaAll our former experience with application of quantum theory seems to say that what is predicted by quantum formalism must occur in the laboratory. But the essence of quantum formalism-entanglement, recognized by Einstein, Podolsky, Rosen, and Schrödinger-waited over 70 years to enter laboratories as a new resource as real as energy. This holistic property of compound quantum systems, which involves nonclassical correlations between...
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Cartoon computation: Quantum-like algorithms without quantum mechanics
PublikacjaZaproponowano formalizm prowadzący do algorytmów analogicznych do kwantowych, lecz wykorzystujący jedynie struktury geometryczne. Jako przykład sformułowano odpowiednik kwantowego algorytmu Deutscha-Jozsy.
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Information transfer during the universal gravitational decoherence
PublikacjaRecently Pikovski et al. (Nat Phys 11:668, 2015) have proposed in an intriguing universal decoherence mechanism, suggesting that gravitation may play a conceptually important role in the quantum-to-classical transition, albeit vanishingly small in everyday situations. Here we analyze information transfer induced by this mechanism. We show that generically on short time-scales, gravitational decoherence leads to a redundant information...
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Redundant information encoding in QED during decoherence
PublikacjaBroadly understood decoherence processes in quantum electrodynamics, induced by neglecting either the radiation [L. Landau, Z. Phys. 45, 430 (1927)] or the charged matter [N. Bohr and L. Rosenfeld, K. Danske Vidensk. Selsk, Math.-Fys. Medd. XII, 8 (1933)], have been studied from the dawn of the theory. However, what happens in between, when a part of the radiation may be observed, as is the case in many real-life situations, has...
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On mixed states entanglement and quantum communication: aspects of quantum channels theory
PublikacjaDokonano przeglądu związków miedzy stanami kwantowymi oraz kwantowymi kanałami. Wykazano, że istnienie nietypowych korelacji kwantowych (splątanie związane typu NPT) w pewnych sytuacjach pociąga za sobą nieaddytywność pojemności kanałów kwantowych.
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Purely quantum superadditivity of classical capacities of quantum multiple access channels
PublikacjaWe are studying classical capacities of quantum memoryless multiaccess channels in geometric terms and we are revealing a break of additivity of the Holevo-like capacity. This effect is a purely quantum mechanical one, since, as we point out, the capacity regions of all classical memoryless multiaccess channels are additive. It is the first such effect revealed in the field of classical information transmission via quantum channels.
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Dynamics of quantum entanglement
PublikacjaA model of discrete dynamics of entanglement of a bipartite quantum state is considered. It involves a global unitary dynamics of the system and periodic actions of local bistochastic or decaying channel. For initially pure states the decay of entanglement is accompanied by an increase of von Neumann entropy of the system. We observe and discuss revivals of entanglement due to unitary interaction of subsystems. For some mixed states...
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Are quantum correlations symmetric?
PublikacjaWe provide operational definition of symmetry of entanglement: An entangled state contains symmetric entanglement if its subsystems can be exchanged (swapped) by means of local operations and classical communication. We show that in general states have asymmetric entanglement. This allows to construct nonsymmetric measure of entanglement, and a parameter that reports asymmetry of entanglement contents of quantum state. We propose...
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Quantum entanglement in time
PublikacjaIn this paper we present a concept of quantum entanglement in time in a context of entangled consistent histories. These considerations are supported by presentation of necessary tools closely related to those acting on a space of spatial multipartite quantum states. We show that in similarity to monogamy of quantum entanglement in space, quantum entanglement in time is also endowed with this property for a particular history....
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Quantum origins of objectivity
PublikacjaIn spite of all of its successes, quantum mechanics leaves us with a central problem: How does nature create a bridge from fragile quanta to the objective world of everyday experience? Here we find that a basic structure within quantum mechanics that leads to the perceived objectivity is a so-called spectrum broadcast structure. We uncover this based on minimal assumptions, without referring to any dynamical details or a concrete...
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Quantum privacy witness
PublikacjaWhile it is usually known that the mean value of a single observable is enough to detect entanglement or its distillability, the counterpart of such an approach in the case of quantum privacy has been missing. Here we develop the concept of a privacy witness, i.e., a single observable that may detect the presence of the secure key even in the case of bound entanglement. Then we develop the notion of secret-key estimation based...
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Correlated electrons and transport in a quantum point contact and in a double-quantum-dot system
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Advances in Quantum Chemistry
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EPJ Quantum Technology
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Quantum Science and Technology
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Quantum Beam Science
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Advanced Quantum Technologies
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QUANTUM INFORMATION & COMPUTATION
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PROGRESS IN QUANTUM ELECTRONICS
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AVS Quantum Science
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IET Quantum Communication
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Radiophysics and Quantum Electronics
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Quantum Machine Intelligence
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Direct detection of quantum entanglement
PublikacjaBasing on positive maps separability criterion we propose the experimentally viable, direct detection of quantum entanglement. It is efficient and does not require any a priori knowledge about the state. For two qubits it provides a sharp (i.e., “if and only if”) separability test and estimation of amount of entanglement. We view this method as a new form of quantum computation, namely, as a decision problem with quantum data structure.
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Direct detection of quantum entanglement
PublikacjaPoddano dyskusji teorię splątania w kontekście historycznym. Omówiono detekcję splątania przy użyciu sieci złożonej z bramek kwantowych.
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Probing the structure of quantum mechanics
PublikacjaWstęp do problemów dotyczących struktury mechaniki kwantowej, a w szczegółności związanych z jej nieliniowością, nielokalnością, a także problemami aks-jomatyzacji i wykorzystaniem zjawisk kwantowych do budowy komuterów.
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A macroscopic device for quantum computation
PublikacjaPrzeanalizowano mechaniczny model kwantowego układu 2-bitowego. Model jest zilustrowany algorytmem Deutscha i Arvinda.
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Hybrid no-signaling-quantum correlations
PublikacjaFundamental investigations in non-locality have shown that while the no-signaling principle alone is not sufficient to single out the set of quantum non-local correlations, local quantum mechanics and no-signaling together exactly reproduce the set of quantum correlations in the two-party Bell scenario. Here, we introduce and study an intermediate hybrid no-signaling quantum set of non-local correlations that we term HNSQ in the...
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The symmetric extendibility of quantum states
PublikacjaStudies on the symmetric extendibility of quantum states have become particularly important in the context of the analysis of one-way quantum measures of entanglement, and the distillability and security of quantum protocols. In this paper we analyze composite systems containing a symmetric extendible part, with particular attention devoted to the one-way security of such systems. Further, we introduce a new one-way entanglement...
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Long-distance quantum communication over noisy networks without long-time quantum memory
PublikacjaThe problem of sharing entanglement over large distances is crucial for implementations of quantum cryptography. A possible scheme for long-distance entanglement sharing and quantum communication exploits networks whose nodes share Einstein-Podolsky-Rosen (EPR) pairs. In Perseguers et al. [Phys. Rev. A 78, 062324 (2008)] the authors put forward an important isomorphism between storing quantum information in a dimension D and transmission...
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INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY
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The decay of quantum correlations between quantum dot spin qubits and the characteristics of its magnetic-field dependence
PublikacjaWe address the question of the role of quantum correlations beyond entanglement in the context of quantum magnetometry. We study the evolution of the rescaled variant of the geometric quantum discord of two electron-spin qubits interacting with an environment of nuclear spins via the hyperfine interaction. We have found that quantum correlations display a strong magnetic-field sensitivity which can be utilized for decoherence-driven...
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Macroscopic models for quantum systems and computers
PublikacjaOpisano układy makroskopowe realizujące dwubitowe operacje kwantowe.
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TelePOVM - A generalized quantum teleportation scheme.
PublikacjaPokazano, że kwantowa teleportacja jest specjalnym przypadkiem uogólnionej nielokalności EPR.
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Thermodynamical approach to quantifying quantum correlations
PublikacjaWe consider the amount of work which can be extracted from a heat bath using a bipartite state ρ shared by two parties. In general it is less then the amount of work extractable when one party is in possession of the entire state. We derive bounds for this “work deficit” and calculate it explicitly for a number of different cases. In particuar, for pure states the work deficit is exactly equal to the distillable entanglement of...
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Correlation experiments in nonlinear quantum mechanics
PublikacjaPokazano w jaki sposób należy obliczać wieloczasowe i wielocząstkowe funkcje korelacyjne w nieliniowej mechanice kwantowej, aby zagwarantować lokalność formalizmu.
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Eigenchannel method in quantum potential scattering.
PublikacjaUogólniono metodę fal cząstkowych na przypadek kwantowego rozpraszania na dowolnym potencjale krótkozasięgowym. Zaprezentowano formalizm ogólny oraz jego zastosowania do cząstek Schrodingera i Duraca.
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No Quantum Realization of Extremal No-Signaling Boxes
PublikacjaThe study of quantum correlations is important for fundamental reasons as well as for quantum communication and information processing tasks. On the one hand, it is of tremendous interest to derive the correlations produced by measurements on separated composite quantum systems from within the set of all correlations obeying the no-signaling principle of relativity, by means of information-theoretic principles. On the other hand,...