Quantum mechanics: The Bayesian theory generalized to the space of Hermitian matrices
We consider the problem of gambling on a quantum experiment and enforce rational behavior by a few rules. These rules yield, in the classical case, the Bayesian theory of probability via duality theorems. In our quantum setting, they yield the Bayesian theory generalized to the space of Hermitian matrices. This very theory is quantum mechanics: in fact, we derive all its four postulates from the generalized Bayesian theory. This implies that quantum mechanics is self consistent. It also leads us to reinterpret the main operations in quantum mechanics as probability rules: Bayes' rule (measurement) marginalization (partial tracing) independence (tensor product) To say it with a slogan, we obtain that quantum mechanics is the Bayesian theory in the complex numbers.