11,266 research outputs found

    Quantum gambling using mesoscopic ring qubits

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    Quantum Game Theory provides us with new tools for practising games and some other risk related enterprices like, for example, gambling. The two party gambling protocol presented by Goldenberg {\it et al} is one of the simplest yet still hard to implement applications of Quantum Game Theory. We propose potential physical realisation of the quantum gambling protocol with use of three mesoscopic ring qubits. We point out problems in implementation of such game.Comment: 4 pages, 1 figure, poster during XXX Intern. Conf. of Theoretical Physics, Electron correlations in nano- and microsystems, Ustron 9-14 September 2006. Minor corrections, references added; to appear in physica status solidi

    Quantum 2-Body Hamiltonian for Topological Color Codes

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    We introduce a two-body quantum Hamiltonian model with spins-\half located on the vertices of a 2D spatial lattice. The model exhibits an exact topological degeneracy in all coupling regimes. This is a remarkable non-perturbative effect. The model has a Z2×Z2\Z_2\times \Z_2 gauge group symmetry and string-net integrals of motion. There exists a gapped phase in which the low-energy sector reproduces an effective topological color code model. High energy excitations fall into three families of anyonic fermions that turn out to be strongly interacting. All these, and more, are new features not present in honeycomb lattice models like Kitaev model.Comment: Cotribution to the Proceedings of the Scala Conference 2009 (Cortina, Italy). Special Issue dedicated to Prof. Prof. Tombesi, on occasion of his seventieth birthday. Editors: D. Vitali, I Marzoli, S. Mancini, G. Di Giuseppe. "Fortschritte der Physik

    Variable Bias Coin Tossing

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    Alice is a charismatic quantum cryptographer who believes her parties are unmissable; Bob is a (relatively) glamorous string theorist who believes he is an indispensable guest. To prevent possibly traumatic collisions of self-perception and reality, their social code requires that decisions about invitation or acceptance be made via a cryptographically secure variable bias coin toss (VBCT). This generates a shared random bit by the toss of a coin whose bias is secretly chosen, within a stipulated range, by one of the parties; the other party learns only the random bit. Thus one party can secretly influence the outcome, while both can save face by blaming any negative decisions on bad luck. We describe here some cryptographic VBCT protocols whose security is guaranteed by quantum theory and the impossibility of superluminal signalling, setting our results in the context of a general discussion of secure two-party computation. We also briefly discuss other cryptographic applications of VBCT.Comment: 14 pages, minor correction

    A critical look at strings

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    This is an invited contribution to the Special Issue of "Foundations of Physics" titled "Forty Years Of String Theory: Reflecting On the Foundations". I have been asked to assess string theory as an outsider, and to compare it with the theory, methods, and expectations in my own field.Comment: 7 page

    Anomalously Slow Cross Symmetry Phase Relaxation, Thermalized Non-Equilibrated Matter and Quantum Computing Beyond the Quantum Chaos Border

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    Thermalization in highly excited quantum many-body system does not necessarily mean a complete memory loss of the way the system was formed. This effect may pave a way for a quantum computing, with a large number of qubits n100n\simeq 100--1000, far beyond the quantum chaos border. One of the manifestations of such a thermalized non-equilibrated matter is revealed by a strong asymmetry around 90^\circ c.m. of evaporating proton yield in the Bi(γ\gamma,p) photonuclear reaction. The effect is described in terms of anomalously slow cross symmetry phase relaxation in highly excited quantum many-body systems with exponentially large Hilbert space dimensions. In the above reaction this phase relaxation is about eight orders of magnitude slower than energy relaxation (thermalization).Comment: Published in SIGMA (Symmetry, Integrability and Geometry: Methods and Applications) at http://www.emis.de/journals/SIGMA
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