Thermodynamics and the structure of quantum theory

Understand

Despite its enormous empirical success, the formalism of quantum theory still raises fundamental questions: why is nature described in terms of complex Hilbert spaces, and what modifications of it could we reasonably expect to find in some regimes of physics? Here we address these questions by studying how compatibility with thermodynamics constrains the structure of quantum theory.

• We employ two postulates that any probabilistic theory with reasonable thermodynamic behavior should arguably satisfy.
• In the framework of generalized probabilistic theories, we show that these postulates already imply important aspects of quantum theory, like self-duality and analogues of projective measurements, subspaces and eigenvalues.
• However, they may still admit a class of theories beyond quantum mechanics.