Proposed split-causality test of the relativity principle
  We propose a test of the principle of relativity, involving quantum signals between two inertial frames. If the principle is upheld, classical causality will appear to be split in a dramatic and emphatic way. We discuss the existence of quantum horizons, which are barriers to the transmission of any form of quantum information. These must occur in any finite time, inter-frame experiment if quantum causality holds. We conclude with some comments on such experiments involving entangled states. 
George Jaroszkiewicz