Quantum key distribution using entangled-photon trains with no basis selection

Conventional quantum key distribution (QKD) protocols include a basis selection process for providing a secure secret key. In contrast, this paper proposes an entanglement-based QKD with no basis selection procedure. Entangled-photon pulse trains with an average photon number less than one per pulse are sent to two legitimate parties, from which a secret key is created utilizing the entanglement nature. Eavesdropping on a transmission line is prevented by a condition of less than one photon per pulse, and sending classically correlated coherent pulses instead of quantum correlated ones is revealed by monitoring coincident count rates.