Causality optional? Testing the "indefinite causal order" superposition

Physicists are testing indefinite causal order, where cause and effect may exist in superposition, upending classical physics. In a 2026 experiment, photons traveled paths where event A caused event B only 47% of the time, with the rest defying sequence—a direct challenge to standard quantum mechanics. The setup achieved a 99.2% confidence level that common-cause explanations fail, making it more rigorous than typical quantum correlation studies. The results suggest that at quantum scales, even time may be negotiable.