  We report the first experimental demonstration of an optical quantum
controlled-NOT gate without any path interference, where the two interacting
path interferometers of the original proposals (Phys. Rev. A {\bf 66}, 024308
(2001), Phys. Rev. A {\bf 65}, 012314 (2002)) have been replaced by three
partially polarizing beam splitters with suitable polarization dependent
transmittances and reflectances. The performance of the device is evaluated
using a recently proposed method (Phys. Rev. Lett. {\bf 94}, 160504 (2005)), by
which the quantum process fidelity and the entanglement capability can be
estimated from the 32 measurement results of two classical truth tables,
significantly less than the 256 measurement results required for full quantum
tomography.
