V.D28 — Operational Distance

The operational distance from subsystem S to target T at depth n_0 is d_op(S,T;n_0) := (1/2)*c * Delta t(n_0, n_2) = (1/2)*c * sum p_k^{-1}, where n_2 is the return depth of a round-trip null intertwiner (radar protocol). It defines a genuine metric on the space of subsystems.