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

TL;DR

This paper investigates how geometric discord, rather than entanglement, serves as a key quantum resource in improving the efficiency of quantum key distribution via twirling, transforming pure states into Werner states.

Contribution

It demonstrates that geometric discord, not entanglement, is the essential resource for reducing error rates in quantum key distribution after twirling.

Findings

Error rate reduced by a factor of 2/3 after twirling.

Entanglement does not increase through the twirling process.

Geometric discord remains a key resource for the protocol.

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.