We demonstrate a technique for performing stochastic simulations of
conditional master equations. The method is scalable for many quantum-field
problems and therefore allows first-principles simulations of multimode bosonic
fields undergoing continuous measurement, such as those controlled by
measurement-based feedback. As examples, we demonstrate a 53-fold speed
increase for the simulation of the feedback cooling of a single trapped
particle, and the feedback cooling of a quantum field with 32 modes, which
would be impractical using previous brute force methods.Comment: 5 pages, 2 figure