  It is well known that the state operator of an open quantum system can be
generically represented as the solution of a time-local equation -- a quantum
master equation.
  Unraveling in quantum trajectories offers a picture of open system dynamics
dual to solving master equations. In the unraveling picture, physical
indicators are computed as Monte-Carlo averages over a stochastic process
valued in the Hilbert space of the system. This approach is particularly
adapted to simulate systems in large Hilbert spaces.
  We show that the dynamics of an open quantum system generically admits an
unraveling in the Hilbert space of the system described by a Markov process
generated by ordinary stochastic differential equations for which rigorous
concentration estimates are available. The unraveling can be equivalently
formulated in terms of norm-preserving state vectors or in terms of linear
``ostensible" processes trace preserving only on average. We illustrate the
results in the case of a two level system in a simple boson environment.
  Next, we derive the state-of-the-art form of the Diosi-Gisin-Strunz Gaussian
random ostensible state equation in the context of a model problem. This
equation provides an exact unraveling of open systems in Gaussian environments.
We compare and contrast the two unravelings and their potential for
applications to quantum error mitigation.
