Measurement-device–independent quantum secure direct communication: Direct quantum communication with imperfect measurement device and untrusted operator

Quantum secure direct communication (QSDC) enables direct message transmission over quantum channels. Loopholes involved in practical apparatus, particularly nonideal measurement devices, provide a potential interface for attacking practical quantum communication. Measurement-device–independent (MDI) QSDC protocols deal with all side-channel attacks on practical measurement devices and directly transmit secret messages over classical channels with both integrity and eavesdropper detection and prevention. We review the recent development of MDI QSDC protocols using both single photons and entangled photon pairs. These two types of MDI QSDC protocols are useful for their respective distinct characters and can be generalized to perform more interesting communication networks