Dall'Arno Michele, Brandsen Sarah, Tosini Alessandro, Buscemi Francesco, Vedral Vlatko
Centre for Quantum Technologies, National University of Singapore, 3 Science Drive 2, 117543 Singapore.
QUIT group, Physics Department, Pavia University, and INFN Sezione di Pavia, via Bassi 6, 27100 Pavia, Italy.
Phys Rev Lett. 2017 Jul 14;119(2):020401. doi: 10.1103/PhysRevLett.119.020401.
A paramount topic in quantum foundations, rooted in the study of the Einstein-Podolsky-Rosen (EPR) paradox and Bell inequalities, is that of characterizing quantum theory in terms of the spacelike correlations it allows. Here, we show that to focus only on spacelike correlations is not enough: we explicitly construct a toy model theory that, while not contradicting classical and quantum theories at the level of spacelike correlations, still displays an anomalous behavior in its timelike correlations. We call this anomaly, quantified in terms of a specific communication game, the "hypersignaling" phenomena. We hence conclude that the "principle of quantumness," if it exists, cannot be found in spacelike correlations alone: nontrivial constraints need to be imposed also on timelike correlations, in order to exclude hypersignaling theories.
量子基础中的一个至关重要的主题，源于对爱因斯坦 - 波多尔斯基 - 罗森（EPR）悖论和贝尔不等式的研究，即根据量子理论所允许的类空关联来刻画量子理论。在此，我们表明仅关注类空关联是不够的：我们明确构建了一个玩具模型理论，该理论虽然在类空关联层面不与经典理论和量子理论相矛盾，但在其类时关联中仍表现出异常行为。我们将这种通过特定通信博弈量化的异常称为“超信号”现象。因此，我们得出结论，“量子性原理”（如果存在的话）不能仅在类空关联中找到：为了排除超信号理论，还需要对类时关联施加非平凡的约束。
