  We compute the quantum Langevin equation (or quantum stochastic differential
equation) representing the action of a quantum heat bath at thermal equilibrium
on a simple quantum system. These equations are obtained by taking the
continuous limit of the Hamiltonian description for repeated quantum
interactions with a sequence of photons at a given density matrix state. In
particular we specialise these equations to the case of thermal equilibrium
states. In the process, new quantum noises are appearing: thermal quantum
noises. We discuss the mathematical properties of these thermal quantum noises.
We compute the Lindblad generator associated with the action of the heat bath
on the small system. We exhibit the typical Lindblad generator that provides
thermalization of a given quantum system.
