  In this paper, we pointed out the separability of the quantum reduced action
in 3D into the sum of three 1D reduced actions depending on the variables $x$,
$y$ and $z$ respectively, and this was done for the case of a potential that
has a cartesian symmetry. This separability was not evident at the first sight.
In addition, the 3D-QSHJE is also separable into three 1D-QSHJE. The free
particle, the spherical and the cylindrical symmetry cases are not discussed in
this paper, however an analogy with the cartesian symmetry case can be down to
show the separability of the total reduced actions into the sum of three 1D
reduced actions for each case.
