Experimental Violation of Two-Party Leggett-Garg Inequalities with Semi-weak Measurements

Understand

We generalize the derivation of Leggett-Garg inequalities to systematically treat a larger class of experimental situations by allowing multi-particle 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 semi-weak polarization measurement based on Fresnel reflection.
• We also point out a non- trivial connection between specific two-party Leggett-Garg inequality violations and convex sums of strange weak values.