Geometric discord: A resource for increments of quantum key distribution through twirling

Abstract

In the present work, we consider a scenario where an arbitrary two-qubit pure state is applied to generate a randomly distributed key via the generalized EPR protocol. Using the twirling procedure to convert the pure state into a Werner state, the error rate of the key can be reduced by a factor of $2/3$. This effect indicates that entanglement is not the sufficient resource of the generalized EPR protocol since it is not increased in the twirling procedure. Instead of entanglement, the geometric discord is suggested to be the general quantum resource for this task.