Possibility to communicate between spatially separated regions, without even a single photon passing between the two parties, is an amazing quantum phenomenon. The possibility of transmitting one value of a bit in such a way, the interaction-free measurement, was known for a quarter of a century. The protocols of full communication, including transmitting unknown quantum states were proposed only a few years ago, but I was arguing that in all these protocols the particle was leaving a weak trace in the transmission channel, the trace larger than the trace left by a single particle passing through the channel. Aharonov and myself found a way to avoid first order trace in the transmission channel but I still have doubts about counterfactuality of the modified protocol.
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This lecture is delivered hybrid, taking place on Zoom and in LG.20 Fry Building.