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We show that the basic dynamical rules of quantum physics can be derived from its static properties and the condition that superluminal communication is forbidden. More precisely, the fact that the dynamics has to be described by linear completely positive maps on density matrices is derived from the following assumptions: (1) physical states are described… (More)

We present a network consisting of quantum gates that produces two imperfect copies of an arbitrary qubit. The quality of the copies does not depend on the input qubit. We also show that for a restricted class of inputs it is possible to use a very similar network to produce three copies instead of two. For qubits in this class, the copy quality is again… (More)

- Vladimír R. Buzek, Mark Hillery
- QCQC
- 1998

We review our recent work on the universal (i.e. input state independent) optimal quantum copying (cloning) of qubits. We present unitary transformations which describe the optimal cloning of a qubit, and we present the corresponding quantum logic network. We also present a network for an optimal quantum copying " machine " (transformation) which produces N… (More)

- V. Bužek, P. L. Knight
- 1997

V. Bužek, 1,2 V. Vedral, 1 M. B. Plenio, 1 P. L. Knight, 1 and M. Hillery 3 Optics Section, The Blackett Laboratory, Imperial College, London SW7 2BZ, England Institute of Physics, Slovak Academy of Sciences, Dubravská cesta 9, 842 28 Bratislava, Slovakia Department of Physics and Astronomy, Hunter College, City University of New York, 695 Park Avenue, New… (More)

- Mário Ziman, Peter Stelmachovic, Vladimír R. Buzek
- Open Syst. Inform. Dynam.
- 2005

- Valerio Scarani, Mário Ziman, Peter Stelmachovic, Nicolas Gisin, Vladimír Buzek
- Physical review letters
- 2002

We study the relaxation of a quantum system towards the thermal equilibrium using tools developed within the context of quantum information theory. We consider a model in which the system is a qubit, and reaches equilibrium after several successive two-qubit interactions (thermalizing machines) with qubits of a reservoir. We characterize completely the… (More)

- F De Martini, V Buzek, F Sciarrino, C Sias
- Nature
- 2002

In classical computation, a 'bit' of information can be flipped (that is, changed in value from zero to one and vice versa) using a logical NOT gate; but the quantum analogue of this process is much more complicated. A quantum bit (qubit) can exist simultaneously in a superposition of two logical states with complex amplitudes, and it is impossible to find… (More)

- Vladimír Buzek, Miguel Orszag, Marián Rosko
- Physical review letters
- 2005

Using tools of quantum information theory we show that the ground state of the Dicke model exhibits an infinite sequence of instabilities (quantum-phase-like transitions). These transitions are characterized by abrupt changes of the bi-partite entanglement between atoms at critical values kappa(j) of the atom-field coupling parameter kappa and are… (More)

- Jan Bouda, Vladimír R. Buzek
- Int. J. Found. Comput. Sci.
- 2003

We show that the distribution of information at the output of the quantum cloner can be efficiently controlled via preparation of the quantum cloner. We present a universal cloning network with the help of which asymmetric cloning can be performed.