Cai--Li Communication Protocol in Noisy Quantum Channel

Since the original Cai--Li protocol Chin. Phys. Lett. 21(2004)601 can be used only in an ideal quantum communication, we present the modified Cai--Li protocol that can be used in the a noisy quantum channel by using Calderbank--Shor--Steane (CSS) codes to correct errors. We also give a tight bound on the connection between information Eve eavesdropped with a measurement attack in line B → A and detection probability, which shows that the Cai--Li protocol can be used as a quasisecure direct quantum communication.