  Usually it is assumed that quantum dense coding is due to quantum
entanglement between two parties. We show that this phenomenon has its origin
in {\em correlations} between two parties rather than simply in entanglement.
In order to justify our argument we evaluate a capacity of the noiseless
channel for two cases: (1) when Bob performs measurement just on the particle
received from Alice and (2) in the case when he utilizes the whole potential of
the dense coding, that is, he performs the measurement on the received particle
and the particle he had prior to the communication. We also present a simple
classical scenario which might serve as a prototype of the dense coding. We
generalize our results also for qudits.

Quantum Physics