Violation of Bell’s Inequality with Photons from Independent Sources

We report a violation of Bell’s inequality using one photon from a parametric down-conversion source and a second photon from an attenuated laser beam. The two photons were entangled at a beam splitter using the postselection technique of Shih and Alley [Phys. Rev. Lett. 61, 2921 (1988)]. A quantum interference pattern with a visibility of $91\%$ was obtained using the photons from these independent sources, as compared with a visibility of $99.4\%$ using two photons from a central parametric down-conversion source.