New Limits For The Realization Of Quantum Processes In Spacetime

Credit: Vilasini & Renner

Ingrid Fadelli -- Phys.org

Oct. 16, 2024

Bell's theorem, the well-known theoretical framework introduced by John Bell decades ago, delineates the limits of classical physical processes arising from relativistic causality principles. These are principles rooted in Einstein's theory of relativity, which dictate how cause and effect operate in the universe.

Researchers at Inria, Université Grenoble Alpes and ETH Zurich recently set out to investigate whether similar types of limits also apply to quantum processes. Their paper, published in Physical Review Letters (PRL), introduces new theorems that outline fundamental limits that could constrain the realization of quantum experiments in classical background spacetimes.

"Causality is central to how we make sense of the world, but it takes on different forms within two of our key physical theories: quantum theory and general relativity," V. Vilasini, co-author of the paper, told Phys.org.

"In quantum theory, causality concerns how information flows between systems and operations, while in general relativity, it's tied to the structure of spacetime itself. Surprisingly, quantum theory permits processes with 'indefinite causal order' (ICO) where the sequence of events can exist in a superposition."

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