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Research Center for Quantum Information
Institute of Physics, Slovak Academy of Sciences
Dúbravská cesta 9, 84511 Bratislava, Slovakia
Tel: (+421 +2) 20910701
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  18.05.2016 Research publication
Incompatible measurements on quantum causal networks
The existence of incompatible measurements, epitomized by Heisenberg's uncertainty principle, is one of the distinctive features of quantum theory. So far, quantum incompatibility has been studied for measurements that test the preparation of physical systems. Here we extend the notion to measurements that test dynamical processes, possibly consisting of multiple time steps. Such measurements are known as testers and are implemented by interacting with the tested process through a sequence of state preparations, interactions, and measurements. Our first result is a characterization of the incompatibility of quantum testers, for which we provide necessary and sufficient conditions. Then we propose a quantitative measure of incompatibility. We call this measure the robustness of incompatibility and define it as the minimum amount of noise that has to be added to a set of testers in order to make them compatible. We show that (i) the robustness is lower bounded by the distinguishability of the sequence of interactions used by the tester and (ii) maximum robustness is attained when the interactions are perfectly distinguishable. The general results are illustrated in the concrete example of binary testers probing the time evolution of a single-photon polarization.
by Michal Sedlák, Daniel Reitzner, Giulio Chiribella, and Mário Ziman
Phys. Rev. A 93, 052323 (2016) |+++|
APVV-0808-12 (QETWORK), VEGA 2/0125/13 (QUICOST), SASPRO 0055/01/01 (QWIN)
S E M I N A R S | more |
21/06 11:00
Sergey N. Filippov (Moscow, Russia)
Pictorial representation of k-p-divisible dynamical maps

24/06 11:00
Mikko Tukainen (Turku, Finland)
Approximate quantum programming

??/?? 11:00
Martin Schwarz (Berlin, Germany)
Approximating local observables on projected entangled-pair states
V I S I T O R S | history |

13.06-23.06 Sergey N. Filippov
(Laboratory of quantum information processing, Moscow Institute of Physics and Technology, Russia)

13.06-12.07 Ilia Luchnikov
(Laboratory of quantum information processing, Moscow Institute of Physics and Technology, Russia)

19.06-30.06 Mikko Tukainen
(Turku Quantum Center, University of Turku, Finland)

08.08-26.08 David Davalos
(National Autonomous University of Mexico, Mexico City)

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