Polaractivation of Hidden Private Classical Capacity Region of Quantum Channels

Abstract: We define a new phenomenon for communication over noisy quantum channels. The investigated solution is called polaractivation and based on quantum polar encoding. Polaractivation is a natural consequence of the channel polarization effect in quantum systems and makes possible to open the hidden capacity regions of a noisy quantum channel by using the idea of rate increment. While in case of a classical channel only the rate of classical communication can be increased, in case of a quantum channel the channel polarization and the rate improvement can be exploited to open unreachable capacity regions. We demonstrate the results for the opening of private classical capacity-domain. We prove that the method works for arbitrary quantum channels if a given criteria in the symmetric classical capacity is satisfied. We also derived a necessary lower bound on the rate of classical communication for the polaractivation of private classical capacity-domain.