On-demand quantum key distribution using superconducting rings with a mesoscopic Josephson junction

We present a quantum key distribution (QKD) protocol based on long lived coherent states prepared on superconducting rings with a mesoscopic Josephson junction (dc-SQUIDs). This enables storage of the prepared states for long durations before actually performing the key distribution. Our on-demand QKD protocol is closely related to the coherent state based continuous variable quantum key distribution protocol. A detailed analysis of preparation, evolution and different measurement schemes that are required to be implemented on dc-SQUIDs to carry out the QKD is provided. We present two variants of the protocol, one requiring time stamping of states and offering a higher key rate and the other without time stamping and a lower key rate. This is a step towards having non-photon based QKD protocols which will be eventually desirable as photon states cannot be stored for long and therefore the key distribution has to be implemented immediately after photon exchange has occurred. Our protocol offers an innovative scheme to perform QKD and can be realized using current experimental techniques.