  We explore algebraic and dynamical consequences of unraveling general
time-local master equations. We show that the "influence martingale", the
paramount ingredient of a recently discovered unraveling framework, pairs any
time-local master equation with a one parameter family of
Lindblad-Gorini-Kossakowski-Sudarshan master equations. At any instant of time,
the variance of the influence martingale provides an upper bound on the
Hilbert-Schmidt distance between solutions of paired master equations. Finding
the lowest upper bound on the variance of the influence martingale yields an
explicit criterion of "optimal pairing". The criterion independently retrieves
the measure of isotropic noise necessary for the structural physical
approximation of the flow the time-local master equation with a completely
positive flow. The optimal pairing also allows us to invoke a general result on
linear maps on operators (the "commutant representation") to embed the flow of
a general master equation in the off-diagonal corner of a completely positive
map which in turn solves a time-local master equation that we explicitly
determine. We use the embedding to reverse a completely positive evolution, a
quantum channel, to its initial condition thereby providing a protocol to
preserve quantum memory against decoherence. We thus arrive at a model of
continuous time error correction by a quantum channel.
