Common operational interface

Tensor factors and laboratory labels in this declaration are operational interface data. They are not spatial coordinates or a spacetime metric. Conversely, an externally assigned speed, spatial distance, or geometric causal relation must not be hidden inside an “operational” label.

A local instrument consists of completely positive maps $\{{\mathcal{M}}_{a|x}{\}}_a$, with ${\sum }_a{\mathcal{M}}_{a|x}$ trace preserving for each setting $x$. The setting is chosen independently of the process except where a specified adaptive protocol permits otherwise. Unconditional signalling compares complete instruments with the sender's outcome summed, not normalized postselected branches OCB,Beckman.