Rodríguez-Rosario, C. A.Modi, K.Mazzola, L.Aspuru-Guzik, Alan2014-01-312012Rodríguez-Rosario, C. A., K. Modi, L. Mazzola, and Alan Aspuru-Guzik. 2012. “Unification of witnessing initial system-environment correlations and witnessing non-Markovianity.” EPL (Europhysics Letters) 99 (2) (July 1): 20010. doi:10.1209/0295-5075/99/20010. http://dx.doi.org/10.1209/0295-5075/99/20010.0295-50751286-4854http://nrs.harvard.edu/urn-3:HUL.InstRepos:11639527We show the connection between a witness that detects dynamical maps with initial system-environment correlations and a witness that detects non-Markovian open quantum systems. Our analysis is based on studying the role that state preparation plays in witnessing violations of contractivity of open-quantum-system dynamics. Contractivity is a property of some quantum processes where the trace distance of density matrices decrease with time. From this, we show how a witness of initial correlations is an upper bound to a witness of non-Markovianity. We discuss how this relationship shows further connections between initial system-environment correlations and non-Markovianity, at an instance of time, in open quantum systems.en-USdecoherenceopen systemsquantum statistical methodsquantum fluctuationsquantum noisequantum jumpsmeasurement theoryquantum mechanics foundationsJournal Article2014-01-3110.1209/0295-5075/99/20010