We are interested in determining the transmission probability over time, which is obtained by integrating the density in the product region defined as [x P ; +∞], for some sufficiently large x P . For the TDQT calculation, this is straightforward, as every trajectory carries the same probability of 1/n. Accordingly, at any given time t, one need only count the number of trajectories, n trans (t), for which x(C i , t) > x P , and compare with n. Note that for this reason, the dynamical simulation cannot be expected to provide a transmission probability resolution finer than 1/n. Indeed, the exact result is only bound to be between n trans (t)/n and (n trans (t) + 1)/n. Hence, a sensible estimate of the transmission probability is obtained as