Department of Mathematics, University of Zagreb, GF, Kaciceva 26, POB-217, HR-10001 Zagreb, Croatia; firstname.lastname@example.org; http://m3k.grad.hr/pavicic
Atominstitute of the Austrian Universities, Schüttelstraße 115, A-1020 Wien, Austria; email@example.com
Abstract. It is shown that one can preselect with certainty photons in the singlet state from a set of completely unpolarized and independent photons which did not in any way directly interact with each other i without in any way affecting them . The result is based on an experiment which puts together two unpolarized photons from two independent singlet pairs, makes them interfere in the fourth order on a beam splitter so as to preselect the singlet state of the other two photons from the pairs although no polarization measurement has been carried out on the photons coming out from the beam splitter. One can obtain the expectation value for the correlated state of the former two unpolarized photons in the Hilbert space and therefore write down the singlet state for them but one apparently cannot infer the state within the Hilbert space. This might sugest that the Hilbert space is not a maximal model for quantum measurements.
PACS numbers: 03.65.Bz, 42.50.Wm
Keywords: four photon interferometry, quantum optics, quantum nonlocality, quantum teleportation, quantum structures, quantum logic.