EPR quantum key distribution protocols with potential 100% qubit efficiency

Public discussion is a useful way for quantum key distribution protocols to reveal the presence of eavesdroppers. However, to ensure better security, nearly 50% of the transmitted qubits are spent in public discussions. Consequently, the original EPR quantum key distribution protocol provides only 25% qubit efficiency and Deng et al.'s scheme delivers only 50% qubit efficiency. By bringing classical cryptographic techniques into the quantum arena, this work proposes EPR quantum key distribution protocols with a potential of 100% qubit efficiency.