Exploring the limits of no backward in time signalling

TL;DR

This paper introduces a framework to analyze the possibility of future events influencing the past without enabling backward-in-time signaling, connecting to quantum theory and indefinite causal structures.

Contribution

It defines no-backwards-in-time signaling conditions, extending the no-signaling concept to temporal scenarios and clarifying their relation to quantum causal structures.

Findings

Future can affect the past without signaling backwards in time.

The framework relates indefinite causal structures to quantum theory.

Provides a model-independent approach to temporal no-signaling.

Abstract

We present an operational and model-independent framework to investigate the concept of no-backwards-in-time signaling. We define no-backwards-in-time signaling conditions, closely related to the spatial no-signaling conditions. These allow for theoretical possibilities in which the future affects the past, nevertheless without signaling backwards in time. This is analogous to non-local but no-signaling spatial correlations. Furthermore, our results shed new light on situations with indefinite causal structure and their connection to quantum theory.