Researchers have proven that when the order of events is 'superposed,' the standard laws of quantum reality must be rewritten.
March 31, 2026
Original Paper
Complementarity Beyond Definite Causal Order
arXiv · 2603.27780
The Takeaway
In a 'quantum switch,' events can happen in two different time-orders at once (A before B and B before A). This study proves that this temporal messiness creates a unique 'causal coherence' that isn't captured by standard physics, forcing a rethink of the fundamental principles used to describe reality.
From the abstract
Wave--particle duality is a cornerstone of quantum mechanics, traditionally formulated under definite causal order. We investigate how complementarity is modified when the temporal order of operations is coherently superposed, as in the quantum switch. We show that no universal linear additive complementarity relation exists that simultaneously captures path distinguishability, spatial coherence, and coherence between causal orders. This reveals a fundamental separation between spatial and causa