The procedure outline in section IV involves calculating the mutual information between the state of an observer at a fixed point in spacetime and the compound state of the causal past
interface increase between two points in the future.
The loophole that is left proposes that a particle detector's settings may "conspire" with events in the shared causal past
of the detectors themselves to determine which properties of the particle to measure-a scenario that, however far-fetched, implies that a physicist running the experiment does not have complete free will in choosing each detector's setting.
Thus, an event e directly precedes an event e', if and only if no other event e" belonging to E exists, such that e" belongs at the same time to the causal future of e and to the causal past of e'.
Each bit in [PHI](p) identifies a message m in the causal past of p.
x will be some factor in the apparent causal past of the measurement, perhaps something in the past of the measuring device or the experimenter, if one is directly involved.
The general form of such a test is that we need to examine Bell experiments, looking for factors which have not previously been thought relevant, to see whether we can discover a previously unnoticed correlation between the preparation of the particles and some factor in the "causal past" of the measurement.