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Dive into the research topics where Pawel Kurzynski is active.

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Featured researches published by Pawel Kurzynski.


Physical Review A | 2005

Unmodulated spin chains as universal quantum wires

Antoni Wojcik; Tomasz Łuczak; Pawel Kurzynski; Andrzej Grudka; Tomasz Gdala; Małgorzata Bednarska

We study a quantum state transfer between two qubits interacting with the ends of a quantum wire consisting of linearly arranged spins coupled by an excitation conserving, time-independent Hamiltonian. We show that, if we control the coupling between the source and the destination qubits and the ends of the wire, the evolution of the system can lead to an almost perfect transfer even in the case in which all nearest-neighbour couplings between the internal spins of the wire are equal.


Physical Review Letters | 2012

Entropic test of quantum contextuality.

Pawel Kurzynski; Ravishankar Ramanathan; Dagomir Kaszlikowski

We study the contextuality of a three-level quantum system using classical conditional entropy of measurement outcomes. First, we analytically construct the minimal configuration of measurements required to reveal contextuality. Next, an entropic contextual inequality is formulated, analogous to the entropic Bell inequalities derived by Braunstein and Caves [Phys. Rev. Lett. 61, 662 (1988)], that must be satisfied by all noncontextual theories. We find optimal measurements for violation of this inequality. The approach is easily extendable to higher dimensional quantum systems and more measurements. Our theoretical findings can be verified in the laboratory with current technology.


Physical Review A | 2012

Trapping a particle of a quantum walk on the line

Antoni Wojcik; Tomasz Łuczak; Pawel Kurzynski; Andrzej Grudka; Tomasz Gdala; Małgorzata Bednarska-Bzdęga

We observe that changing a phase at a single point in a discrete quantum walk results in a rather surprising localization effect. For certain values of this phase change the possibility of localization strongly depends on the internal coin-state of the walker.


Physics Letters A | 2003

Quantum walks on cycles

Małgorzata Bednarska; Andrzej Grudka; Pawel Kurzynski; Tomasz Łuczak; Antoni Wojcik

We consider asymptotic behaviour of a Hadamard walk on a cycle. For the walk which starts with a state in which all the probability is concentrated on one node, we find the explicit formula for the limiting distribution and discuss its asymptotic behaviour when the length of the cycle tends to infinity. We also demonstrate that for a carefully chosen initial state, the limiting distribution of a quantum walk on cycle can lie further away from the uniform distribution than its initial state.


Physical Review Letters | 2011

Local Realism of Macroscopic Correlations

Ravishankar Ramanathan; Tomasz Paterek; Alastair Kay; Pawel Kurzynski; Dagomir Kaszlikowski

We identify conditions under which correlations resulting from quantum measurements performed on macroscopic systems (systems composed of a number of particles of the order of the Avogadro number) can be described by local realism. We argue that the emergence of local realism at the macroscopic level is caused by an interplay between the monogamous nature of quantum correlations and the fact that macroscopic measurements do not reveal properties of individual particles.


Physics Letters A | 2008

Relativistic effects in quantum walks : Klein's paradox and zitterbewegung

Pawel Kurzynski

Quantum walks are not only algorithmic tools for quantum computation but also non-trivial models describing various physical processes. The Letter compares one-dimensional version of the free particle Dirac equation with the discrete time quantum walk (DTQW). It is shown that two relativistic effects associated with the Dirac equation, namely zitterbewegung (quivering motion) and Kleins paradox, are manifested in DTQW. A special case of DTQW for Lorentz invariance not satisfied in the corresponding continuous limit is considered. The effects are examined.


Physical Review A | 2012

Contextuality of almost all qutrit states can be revealed with nine observables

Pawel Kurzynski; Dagomir Kaszlikowski

We propose a test of quantum contextuality for a single three-level system that uses nine projective measurements. It has a form of an inequality that has to be satisfied by any non-contextual theory and which is violated by any quantum state, except for the maximally mixed one. Due to the fact that there is only a single state that does not exhibit contextuality, it is natural to ask what the difference between state-independent tests and the one proposed here is.


Scientific Reports | 2013

An experimental proposal for revealing contextuality in almost all qutrit states

Jayne Thompson; Robert Pisarczyk; Pawel Kurzynski; Dagomir Kaszlikowski

Contextuality is a foundational phenomenon underlying key differences between quantum theory and classical realistic descriptions of the world. Here we propose an experimental test which is capable of revealing contextuality in all qutrit systems, except the completely mixed state, provided we choose the measurement basis appropriately. The 3-level system is furnished by the polarization and spatial degrees of freedom of a single photon, which encompass three orthogonal modes. Projective measurements along rays in the 3-dimensional Hilbert space are made by linear optical elements and detectors which are sensitive to single mode. We also discuss the impact of detector inefficiency and losses and review the theoretical foundations of this test.


Physical Review Letters | 2008

Is There Contextuality for a Single Qubit

Andrzej Grudka; Pawel Kurzynski

Cabello and Nakamura have shown [A. Cabello, Phys. Rev. Lett. 90, 190401 (2003)10.1103/PhysRevLett.90.190401] that the Kochen-Specker theorem can be applied to two-dimensional systems if one uses positive operator-valued measures (POVM). We show that the contextuality in their models is not of the Kochen-Specker type, but it is rather a result of not keeping track of the whole system on which the measurement is performed. This is connected to the fact that there is no one-to-one correspondence between the POVM elements and projectors on the extended Hilbert space, and the same POVM element has to originate from two different projectors when used in Cabello-Nakamura models. Moreover, we propose a hidden-variable formulation of the above models.


Journal of Physics A | 2010

Mutually unbiased bases and complementary spin 1 observables

Pawel Kurzynski; Wawrzyniec Kaszub; Mikołaj Czechlewski

The two observables are incompatible if they cannot be measured simultaneously; however, they become maximally incompatible (complementary) if their eigenstates are mutually unbiased. Only then does the measurement of one observable give no information about the other observable. The spin projection operators onto three mutually orthogonal directions are complementary only for spin 1/2. For higher spin numbers the corresponding eigenstates are no longer unbiased. In this work we examine the properties of spin 1 mutually unbiased bases (MUB) and look for the physical meaning of the corresponding operators. We show that if the computational basis is chosen to be the eigenbasis of the spin projection operator along some direction z, then all the states, which are unbiased to this basis, have to be squeezed. Next, we study the generation and the measurement of MUB states by introducing the Fourier-like transform through spin squeezing. Finally, we try to ascribe some classical interpretation to the operators corresponding to MUB and study what information the observer gains while measuring them. Higher spin numbers are also considered.

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Dagomir Kaszlikowski

National University of Singapore

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Andrzej Grudka

Adam Mickiewicz University in Poznań

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Antoni Wojcik

Adam Mickiewicz University in Poznań

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Jayne Thompson

National University of Singapore

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Małgorzata Bednarska

Adam Mickiewicz University in Poznań

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Tomasz Łuczak

Adam Mickiewicz University in Poznań

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Tomasz Gdala

Adam Mickiewicz University in Poznań

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