Operational causality in spacetime
Abstract
The nosignaling principle preventing superluminal communication is a limiting paradigm for physical theories. Within the informationtheoretic framework it is commonly understood in terms of admissible correlations in composite systems. Here we unveil its complementary incarnation—the "dynamical nosignaling principle"—which forbids superluminal signaling via measurements on simple physical objects (e.g., particles) evolving in time. We show that it imposes strong constraints on admissible models of dynamics. The posited principle is universal; it can be applied to any theory (classical, quantum, or postquantum) with welldefined rules for calculating detection statistics in spacetime. As an immediate application we show how one could exploit the Schrödinger equation to establish a fully operational superluminal protocol in the Minkowski spacetime. This example illustrates how the principle can be used to identify the limits of applicability of a given model of quantum or postquantum dynamics.
 Publication:

Physical Review A
 Pub Date:
 April 2020
 DOI:
 10.1103/PhysRevA.101.042128
 arXiv:
 arXiv:1902.05002
 Bibcode:
 2020PhRvA.101d2128E
 Keywords:

 Quantum Physics;
 General Relativity and Quantum Cosmology;
 Mathematical Physics;
 81P16 (Primary);
 81P15;
 28E99;
 60B05 (Secondary)
 EPrint:
 10 pages (including 3 pages of Supplemental Material), 5 figures, 1 table