CONTROLLED DENSE CODING VIA GHZ-CLASS STATE

Abstract

A controlled quantum dense coding protocol with GHZ-class state is proposed. In this case the sender (Alice) can send information to the receiver (Bob), whereas the supervisor (Cliff) can control the quantum channel between Alice and Bob via his local measurement. The amount of classical information is shown to be controlled by the supervisor through adjustments of the local measurement angles and depend on the coefficients of the original GHZ-class state. We also give two concrete methods for Alice to deal with one of Cliff's measurement result which is more complicated.