Freiburg 2019 – scientific programme

Sessions | Days | Selection | Search | Updates | Downloads | Help

FM: Fall Meeting

FM 11: Entanglement: Many-Body States I

FM 11.7: Talk

Monday, September 23, 2019, 15:45–16:00, 2004

Entanglement witnesses 2.0 : entanglement witnesses can be compressed — •Joonwoo Bae¹, Dariusz Chruscinski², and Beatrix Hiesmayr³ — ¹School of Electrical Engineering, Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro, Yuseong-gu, Daejeon 34141, Republic of Korea — ²Institute of Physics, Faculty of Physics, Astronomy, and Informatics, Nicolaus Copernicus University, Grudziadzka 5, 87-100 Torun, Poland — ³University of Vienna, Faculty of Physics, Boltzmanngasse 5, 1090 Vienna, Austria

An entanglement witness is an observable detecting entanglement for a subset of states. We present a framework that makes an entanglement witness twice as powerful due to the general existence of a second (lower) bound, in addition to the (upper) bound of the very definition. This second bound, if non-trivial, is violated by another subset of entangled states. Differently stated, we prove via the structural physical approximation that two witnesses can be compressed into a single one. Consequently, our framework shows that any entanglement witness can be upgraded to a witness 2.0. The generality and its power are demonstrate by applications to bipartite and multipartite qubit/qudit systems.