Causally neutral quantum physics

Understand

In fundamental theories that accounts for quantum gravitational effects, the spacetime causal structure is expected to be quantum uncertain.

• Previous studies of quantum causal structure focused on finite-dimensional systems.
• Here we present an algebraic framework that incorporates both finite- and infinite-dimensional systems including quantum fields.
• Thanks to the absence of a definite spacetime causal structure, Lagrangian quantum field theories can be studied on a quantum superposition of spacetimes with a point identification structure.