  We consider the Symmetric Simple Exclusion Process (SSEP) on the segment with
two reservoirs of densities $p, q \in (0,1)$ at the two endpoints. We show that
the system exhibits cutoff with a diffusive window, thus confirming a
conjecture of Gantert, Nestoridi, and Schmid in \cite{Gantert2020}. In
particular, our result covers the regime $p \neq q$, where the process is not
reversible and there is no known explicit formula for the invariant measure.
Our proof exploits the information percolation framework introduced by Lubetzky
and Sly, the negative dependence of the system, and an anticoncentration
inequality at the conditional level. We believe this approach is applicable to
other models.
