title: Locality and universality of quantum memory effects.
abstract: The modeling and analysis of the dynamics of complex systems often requires to employ non-Markovian stochastic processes. While there is a clear and well-established mathematical definition for non-Markovianity in the case of classical systems, the extension to the quantum regime recently caused a vivid debate, leading to many different proposals for the characterization and quantification of memory effects in the dynamics of open quantum systems. Here, we derive a mathematical representation for the non-Markovianity measure based on the exchange of information between the open system and its environment, which reveals the locality and universality of non-Markovianity in the quantum state space and substantially simplifies its numerical and experimental determination. We further illustrate the application of this representation by means of an all-optical experiment which allows the measurement of the degree of memory effects in a photonic quantum process with high accuracy.
authors.affiliation: 1] Key Laboratory of Quantum Information, University of Science and Technology of China, CAS, Hefei, 230026, China [2].
authors.forename: B-H
authors.initials: BH
authors.lastname: Liu
authors.affiliation: 1] Physikalisches Institut, Universität Freiburg, Hermann-Herder-Straße 3, D-79104 Freiburg, Germany [2].
authors.forename: S
authors.initials: S
authors.lastname: Wißmann
authors.affiliation: Key Laboratory of Quantum Information, University of Science and Technology of China, CAS, Hefei, 230026, China.
authors.forename: X-M
authors.initials: XM
authors.lastname: Hu
authors.affiliation: Key Laboratory of Quantum Information, University of Science and Technology of China, CAS, Hefei, 230026, China.
authors.forename: C
authors.initials: C
authors.lastname: Zhang
authors.affiliation: Key Laboratory of Quantum Information, University of Science and Technology of China, CAS, Hefei, 230026, China.
authors.forename: Y-F
authors.initials: YF
authors.lastname: Huang
authors.affiliation: Key Laboratory of Quantum Information, University of Science and Technology of China, CAS, Hefei, 230026, China.
authors.forename: C-F
authors.initials: CF
authors.lastname: Li
authors.affiliation: Key Laboratory of Quantum Information, University of Science and Technology of China, CAS, Hefei, 230026, China.
authors.forename: G-C
authors.initials: GC
authors.lastname: Guo
authors.affiliation: Turku Centre for Quantum Physics, Department of Physics and Astronomy, University of Turku, FI-20014 Turun yliopisto, Finland.
authors.forename: A
authors.initials: A
authors.lastname: Karlsson
authors.affiliation: Turku Centre for Quantum Physics, Department of Physics and Astronomy, University of Turku, FI-20014 Turun yliopisto, Finland.
authors.forename: J
authors.initials: J
authors.lastname: Piilo
authors.affiliation: Physikalisches Institut, Universität Freiburg, Hermann-Herder-Straße 3, D-79104 Freiburg, Germany.
authors.forename: H-P
authors.initials: HP
authors.lastname: Breuer