Entanglement and Optimal Timing in Discriminating Quantum Dynamical Processes

I investigate the problem of optimally discriminating between two open quantum dynamical processes in a single-shot scenario, with the goal of minimizing the error probability of identification. This task involves optimising both the input state – potentially entangled with an ancillary system that remains isolated from the dynamics – and the time at which the resulting time-dependent quantum channels, induced by the two distinct dynamical maps, becomes most distinguishable. To illustrate the complexity and richness of this problem, I focus on Pauli dynamical maps and their associated families of time-dependent Pauli channels. I identify a regime in which separable strategies require waiting indefinitely for the dynamics to reach the stationary state, whereas entangled input states enable optimal discrimination at a finite time, with a strict reduction in error probability. These results highlight the crucial interplay between entanglement and timing in enhancing the distinguishability of quantum dynamical processes.