Robustness of two-way quantum communication protocols against Trojan   horse attack
  We discuss the robustness of two-way quantum communication protocols against Trojan horse attack and introduce a novel attack, delay-photon Trojan horse attack. Moreover, we present a practical way for two-way quantum communication protocols to prevent the eavesdropper from stealing the information transmitted with Trojan horse attacks. It means that two-way quantum communication protocols is also secure in a practical application. 
Fu-Guo Deng, Ping Zhou, Xi-Han Li, Chun-Yan Li, and Hong-Yu Zhou