Multichannel hybrid quantum cryptography for submarine opticalcommunications

We present a multichannel hybrid quantum cryptography approach intended for submarine quantum optical communications between Alice and Bob separated by a distance beyond the current QKD possibilities, each located on a coastline. It is based on the difficulty of simultaneous access to <i>M</i> optical submarine channels. The optical lines from the coastline, and ideally to the end of the continental shelf, are governed by the quantum properties of the light under an autocompensating high-dimensional discrete-modulation continuous variable QKD protocol. The hybrid approach consists of combining several secret keys of <i>M</i> channels and introducing extra layers of security, passive and/or active, on the non-quantum optical lines located beyond the continental shelf.