Nonsecret correlations can be used to distribute secrecy

Abstract

A counterintuitive result in entanglement theory was shown by Cubitt [Phys. Rev. Lett. 91, 037902 (2003)], namely, that entanglement can be distributed by sending a separable state through a quantum channel. In this work, following an analogy between the entanglement and secret-key distillation scenarios, we derive its classical analog: secrecy can be distributed by sending nonsecret correlations through a private channel. This strengthens the close relation between entanglement and secrecy.