Abstract
We derive the equations of quantum mechanics and quantum thermodynamics from the assumption that a quantum system can be described by an underlying classical system of particles. Each component φ_j of the wave vector is understood as a stochastic complex variable whose real and imaginary parts are proportional to the coordinate and momentum associated to a degree of freedom of the underlying classical system. From the classical stochastic equations of motion, we derive a general equation for the covariance matrix of the wave vector which turns out to be of the Lindblad type. When the noise changes only the phase of φ_j, the Schr\"odinger and the quantum Liouville equation are obtained. The component ψ_j of the wave vector obeying the Schr\"odinger equation is related to stochastic wave vector by |ψ_j|²=|φ_j|².