**Mladen Pavicic**

*Institut für Theoretische Physik,
TU Berlin, Hardenbergstraße 36, D-10623 Berlin 12, Germany
*

*Atominstitute of the Austrian Universities,
Schüttelstraße 115, A-1020 Wien, Austria; pavicic@ati.ac.at
*

*Department of Mathematics, University of Zagreb,
GF, Kaciceva 26, POB-217, HR-10001 Zagreb, Croatia; mpavicic@faust.irb.hr; http://m3k.grad.hr/pavicic
*

** Abstract. **A nonclassical
feature of the fourth order interference at a beam
splitter, that genuine photon spin singlets are emitted in predetermined
directions even when incident photons are unpolarized, has been used
in a proposal for an experiment that imposes quantum spin correlation
on truly independent photons. In the experiment two photons from two
such singlets interfere at a beam splitter, and as a result the other
two photons - which nowhere interacted and whose paths nowhere
crossed - exhibit a 100% correlation in polarization, even when
no polarization has been measured in the first two photons. The
propsed experiment permits closure of the remaining loopholes in the
Bell theorem proof, reveals the quantum nonlocality as a property of
selection, and pioneers an experimental procedure for exact preparation
of unequal superposition.

**PACS numbers: **: 42.50.Wm, 03.65.Bz

**Keywords: **four photon interferometry,
quantum optics, quantum nonlocality, quantum teleportation,
Bell experiment.