When quantum boundary meets the non-signaling boundary
Kai-Siang Chen1*, Junyi Wu2, Gelo Noel M. Tabia1,3, Pei-Sheng Lin1, C. Jebarathinam4, Yeong-Cherng Liang1
1Department of Physics and Center for Quantum Frontiers of Research & Technology (QFort), National Cheng Kung University, Tainan 701, Taiwan
2Department of Physics, Graduate School of Science, The University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-0033, Japan
3Center for Quantum Technology, National Tsing Hua University, Hsinchu 300, Taiwan
4Center for Theoretical Physics, Polish Academy of Sciences, Aleja Lotników 32/46, 02-668 Warsaw, Poland
* Presenter:Kai-Siang Chen, email:c24056083@gs.ncku.edu.tw
In the studies of device-independent quantum information, correlations between local measurement outcomes observed by spatially separated parties in a Bell test play a fundamental role. In particular, it is of paramount importance to characterize the various sets of correlations attained by locally measuring composite systems constrained by different physical principles. Among them, the principle of relativistic causality dictates that all correlations must satisfy the so-called non-signaling conditions. On the other hand, the principle of local causality demands, instead, that all such correlations be Bell-local. Even though it is long known that the set of correlations allowed in quantum theory lies strictly between those characterized by these two principles, many questions concerning the geometry of these sets remain unanswered. Here, we report progress on this problem by fully characterizing when the boundary of the quantum set may coincide with the boundary of the non-signaling set in the simplest Bell scenario.

Keywords: Device-Independent, Bell-Nonlocality, Non-Signaling