Quantum Key Distribution against Trojan Horse Attacks

Realistic experimental apparatus of quantum cryptography are imperfect,
which may be utilized by a potential eavesdropper to eavesdrop on the
communication. We show that quantum communication may be improved with
quantum teleportation and entanglement swapping, which is robustly secure
against the most general Trojan horse attacks. Our scheme is not an
improvement of the communication apparatus, but the improvement of
quantum communication protocol itself. We show that our modified schemes
may be implemented with current technology.