Quantum Whispers

Abstract

It is shown that with the use of entanglement a specific two party communication task can be done with a systematically smaller expected error than any possible classical protocol could do. The example utilises the very tight correlation between separate spin measurements on a singlet state for small differences in the angles of these two measurements. An extension of this example to many parties arranged in a row with only local, one-to-one communication (whispering) is then considered. It is argued that in this scenario there exists no reliable classical protocol, whereas in the quantum case there does.