Modified double-slit experiment suggests possibility of hidden variables

New Scientist : The idea that there are nonlocal hidden variables that define quantum behaviors was suggested by David Bohm in 1952, but it has generally fallen out of favor. A key strike against the theory came in a 1992 thought experiment involving a modified version of the famous double-slit experiment with a detector in front of each slit. Now Aephraim Steinberg of the University of Toronto and colleagues have converted the experiment from thought to reality, and they say the results may vindicate Bohm and his hidden variables. The researchers sent one of a pair of entangled photons through an apparatus that directed the photon to one of two slits depending on the photon’s polarization. But as the photon passed through the apparatus, the polarization of the entangled partner changed, suggesting that detectors outside the slits are unreliable in any realization of the thought experiment.