Experimental entanglement of temporal order

Understand

The study of causal relations has recently been applied to the quantum realm, leading to the discovery that not all physical processes have a definite causal structure.

• While indefinite causal processes have previously been experimentally shown, these proofs relied on the quantum description of the experiments.
• Yet, the same experimental data could also be compatible with definite causal structures within different descriptions.
• Here, we present the first demonstration of indefinite temporal order outside of quantum formalism.