Efficient Distinction between Quantum Direct and Common Causes and its Experimental Verification

TL;DR

This paper introduces the 'Causal Determinant', a new quantum measure that efficiently distinguishes between direct and common causes in quantum systems, validated through experimental verification.

Contribution

The paper proposes the 'Causal Determinant' as a novel, effective tool for identifying quantum causal structures, including more general cases, with experimental validation.

Findings

Successfully discriminates between quantum direct and common causes

Capable of identifying more complex quantum causal structures

Experimental verification confirms the method's validity

Abstract

Identifying the causal structures between two statistically correlated events has been widely investigated in many fields of science. While some of the well-studied classical methods are carefully generalized to quantum version of causal inference for certain cases, an effective and efficient way to detect the more general quantum causal structures is still lacking. Here, we introduce a quantity named `Causal Determinant' to efficiently identify the quantum causal structures between two quantum systems and experimentally verify the validity of the method. According to the causal determinant, the quantum direct cause imposed by an arbitrary unitary operator can be perfectly discriminated with the quantum common cause, in which the two quantum systems share a joint quantum state. In addition, the causal determinant has the capability to discriminate between more general causal structures and predict the range of their parameters. The ability to detect more general quantum causal structures of our method can shed new light on the field of quantum causal inference.