Navegando por Autor "Modi, Kavan"
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Artigo Monogamy of temporal correlations: Witnessing non-Markovianity beyond data processing(American Physical Society, 2020-03-20) Capela, Matheus; Céleri, Lucas C.; Modi, Kavan; Araújo, Rafael Chaves SoutoThe modeling of natural phenomena via a Markov process—a process for which the future is independent of the past, given the present—is ubiquitous in many fields of science. Within this context, it is of foremost importance to develop ways to check from the available empirical data if the underlying mechanism is indeed Markovian. A paradigmatic example is given by data processing inequalities, the violation of which is an unambiguous proof of the non-Markovianity of the process. Here, our aim is twofold. First we show the existence of a monogamy-like type of constraint, beyond data processing, respected by Markov chains. Secondly, we show a connection between the quantification of causality and the violation of both data processing and monogamy inequalities. Apart from its foundational relevance in the study of stochastic processes we also consider the applicability of our results in a typical quantum information setup, showing it can be useful to witness the non-Markovianity arising in a sequence of quantum nonprojective measurementsArtigo Quantum Markov monogamy inequalities(Physical Review A, 2022-08-29) Araújo, Rafael Chaves Souto; Céleri, Lucas Chibebe; Capela, Matheus; Modi, KavanMarkovianity lies at the heart of communication problems. This in turn makes the information-theoretic characterization of Markov processes worthwhile. Data-processing inequalities are ubiquitous in this sense, assigning necessary conditions for all Markov processes. We address here the problem of the information-theoretic analysis of constraints on Markov processes in the quantum regime. We show the existence of a class of quantum data-processing inequalities called here quantum Markov monogamy inequalities. This class of necessary conditions on quantum Markov processes is inspired by its counterpart for classical Markov processes, thus providing a strong link between classical and quantum constraints on Markovianity. We go on to construct a family of multitime quantum Markov monogamy inequalities, based on the process tensor formalism and that exploits multitime correlations. We then show, by means of an explicit example, that the Markov monogamy inequalities can be stronger than the usual quantum data-processing inequalities