Quantum Theory Cannot Violate a Causal Inequality.

Area of Science:

• Quantum mechanics
• Foundations of physics
• Causality

Background:

• Quantum theory permits superpositions of different causal orders.
• Interference effects arise from these superpositions.
• This prompts investigation into potential violations of causal inequalities.

Purpose of the Study:

• To determine if quantum theory can produce results unachievable by classical causal models.
• To investigate if quantum experiments can violate a causal inequality, a temporal analog to Bell inequality violation.

Main Methods:

• Theoretical analysis of quantum experiments involving superpositions of causal orders.
• Comparison of quantum predictions with the capabilities of classical causal models.

Main Results:

• Quantum experiments involving superpositions of causal orders can be simulated by classical causal models.
• A violation of a causal inequality, analogous to Bell inequality violation, is not possible.

Conclusions:

• Quantum phenomena related to causal order do not violate classical causal inequalities.
• The findings indicate that classical causal models are sufficient to describe these quantum effects, unlike in the case of nonlocality.