Stochastic pure state representation for open quantum systems
  We show that the usual master equation formalism of Markovian open quantum systems is completely equivalent to a certain state vector formalism. The state vector of the system satisfies a given frictional Schr\"odinger equation except for random instant transitions of discrete nature. Hasse's frictional Hamiltonian is recovered for the damped harmonic oscillator. 
Lajos Di\'osi
quant-ph