  Recently a quite stimulating paper [1] dealing with the possibility of
exploiting the nonlocal aspects of a superposition of states of a single photon
appeared. We regard as greatly relevant the results which have been obtained.
However we think that the presentation of the matter and the way to derive the
conclusion are not fully satisfactory and do not put the necessary emphasis on
some subtle basic aspects like locality and realism. In view of its interest we
consider it useful to reconsider the line of reasoning of ref.[1] and to derive
once more its results by following a procedure which seems to us more lucid and
which makes fully clear the role of the various conceptual aspects of the
treatment. We hope that our analysis will contribute to clarify and to deepen
the interesting results of ref.[1].
