Modern communication networks can be flexibly shaped and controlled using Software Defined Networking (SDN) paradigm. However, besides unprecedented functional benefits, this solution exploits an architectural single point of failure. Securing the communication among SDN functional element is therefore a critical requirement for improving the network reliability. A novel approach to secure communications is provided by Quantum Key Distribution (QKD) that is a physical layer technology capable to securely deliver symmetric encryption keys leveraging on quantum physic properties. Our research demonstrates how to provide unconditionally secure communication at SDN level dramatically improving the reliability of the communication network itself.