Quantum superpositions of "common-cause" and "direct-cause" causal structures

TL;DR

This paper explores quantum superpositions of causal structures, proposing an implementation involving spatial superposition and relativistic effects, and develops methods to distinguish quantum from classical causal relations.

Contribution

It introduces a framework for superposing causal structures and provides an efficient method to identify genuinely quantum causal relations versus classical mixtures.

Findings

Proposes a superposition of causal structures involving relativistic effects.

Develops a computational method to distinguish quantum from classical causality.

Suggests experimental designs for verifying quantum causal nonclassicality.

Abstract

The constraints arising for a general set of causal relations, both classically and quantumly, are still poorly understood. As a step in exploring this question, we consider a coherently controlled superposition of "direct-cause" and "common-cause" relationships between two events. We propose an implementation involving the spatial superposition of a mass and general relativistic time dilation. Finally, we develop a computationally efficient method to distinguish such genuinely quantum causal structures from classical (incoherent) mixtures of causal structures and show how to design experimental verifications of the nonclassicality of a causal structure.