Experimental violation of two-party Leggett-Garg inequalities with semiweak measurements

Phys Rev Lett. 2011 Jan 28;106(4):040402. doi: 10.1103/PhysRevLett.106.040402. Epub 2011 Jan 24.


We generalize the derivation of Leggett-Garg inequalities to systematically treat a larger class of experimental situations by allowing multiparticle correlations, invasive detection, and ambiguous detector results. Furthermore, we show how many such inequalities may be tested simultaneously with a single setup. As a proof of principle, we violate several such two-particle inequalities with data obtained from a polarization-entangled biphoton state and a semiweak polarization measurement based on Fresnel reflection. We also point out a nontrivial connection between specific two-party Leggett-Garg inequality violations and convex sums of strange weak values.