  In this letter we experimentally implement a single photon Bell test based on
the ideas of S. Tan et al. [Phys. Rev. Lett., vol. 66, 252 (1991)] and L. Hardy
[Phys. Rev. Lett.,vol. 73, 2279 (1994)]. A double heterodyne measurement is
used to measure correlations in the Fock space spanned by zero and one photons.
Local oscillators used in the correlation measurement are distributed to two
observers by co-propagating it in an orthogonal polarization mode. This method
eliminates the need for interferometrical stability in the setup, consequently
making it a robust and scalable method.
