Schroedinger current for discontinuous states from the first passage time decomposition

Abstract: We revisit the problem of calculating the probability current for discontinuous states, such that may arise in atom trapping or as a result of projective measurements. In the first passage time representation, the problem reduces to evaluation of a localised wave originating from the discontinuity, whose interference with the initial state determines the transfer of probability. Depending on the type of discontinuity, the current behaves as $t^{1/2}$, $t^{3/2}$ or $const(t)$. Our approach generalises earlier work on this subject.