Do the laws of physics prohibit counterfactual communication?

Abstract

It has been conjectured that counterfactual communication is impossible, even for post-selected quantum particles. We strongly challenge this by proposing exactly such a counterfactual scheme where---unambiguously---none of Alice's photons that make it has been to Bob. We demonstrate counterfactuality theoretically and experimentally by means of weak measurements, as well as conceptually using consistent histories. Importantly, the accuracy of Alice learning Bob's bit can be made arbitrarily close to unity with no trace left by Bob on Alice's photon.Comment: Experiment conducted in the lab, showing no weak trace from Bob at either D0 or D1. 5 pages, 5 figure