Modeling observers as physical systems representing the world from within: Quantum theory as a physical and self-referential theory of inference

Understand

In 1929 Szilard pointed out that the physics of the observer may play a role in the analysis of experiments.

• The same year, Bohr pointed out that complementarity appears to arise naturally in psychology where both the objects of perception and the perceiving subject belong to 'our mental content'.
• Here we argue that the formalism of quantum theory can be derived from two related intuitive principles: (i) inference is a physical process performed by physical systems, observers, which are part of the experimental setup---this implies non-commutativity and imaginary-time quantum mechanics; (ii) experiments must be described from a first-person perspective---this leads to self-reference, complementarity, and real-time quantum dynamics.
• This approach sheds new light on the foundations of quantum theory and suggests fundamental equations in physics are typically of second order due to the physical nature of the observer.