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Proceedings Paper

Quantum safe with classical key: physics of open systems from the point view of information theory
Author(s): Mario Ziman; P. Stelmachovic; Vladimir Buzek; Mark Hillery; Valerio Scarani; Nicolas Gisin
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Paper Abstract

We design a universal quantum homogenizer, which is a quantum machine that takes as an input a system qubit initially in the state ? and a set of N reservoir qubits initially prepared in the same state ?. In the homogenizer the system qubit sequentially interacts with the reservoir qubits via the partial swap transformation. The homogenizer realizes, in the limit sense, the transformation such that at the output each qubit is in an arbitratily small neighbourhood of the state ? irrespective of the initial states of the system and the reservoir qubits. This means that the system qubit undergoes an evolution that has a fixed point, which is the reservoir state ?. We also study approximate homogenization when the reservoir is composed of a finite set of identically prepared qubits. The homogenizer allows us to understand various aspects of the dynamics of open systems interacting with environments in non-equilibrium states. In particular, the reversibility vs or irreversibility of the dynamics of the open system is directly linked to specific (classical) information about the order in which the reservoir qubits interacted with the system qubit. This aspect of the homogenizer leads to a model of a quantum safe with a classical combination.We analyze in detail how entanglement between the reservoir and the system is created during the process of quantum homogenization. We show that the information about the initial state of the system qubit is stored in the entanglement between the homogenized qubits.

Paper Details

Date Published: 22 July 2002
PDF: 12 pages
Proc. SPIE 4888, First International Workshop on Classical and Quantum Interference, (22 July 2002); doi: 10.1117/12.475875
Show Author Affiliations
Mario Ziman, Research Ctr. for Quantum Information (Slovak Republic)
P. Stelmachovic, Research Ctr. for Quantum Information (Slovak Republic)
Vladimir Buzek, Research Ctr. for Quantum Information and Masaryk Univ. (Slovak Republic)
Mark Hillery, CUNY/Hunter College (United States)
Valerio Scarani, Univ. de Geneve (Switzerland)
Nicolas Gisin, Univ. de Geneve (Switzerland)

Published in SPIE Proceedings Vol. 4888:
First International Workshop on Classical and Quantum Interference
Jan Perina; Miroslav Hrabovsky; Jaromir Krepelka, Editor(s)

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