  Quantum secure direct communication (QSDC) is the technology to transmit
secret information directly through a quantum channel without neither key nor
ciphertext. It provides us with a secure communication structure that is
fundamentally different from the one that we use today. In this Letter, we
report the first measurement-device-independent(MDI) QSDC protocol with
sequences of entangled photon pairs and single photons. It eliminates security
loopholes associated with the measurement device. In addition, the MDI
technique doubles the communication distance compared to those without using
the technique. We also give a protocol with linear optical Bell-basis
measurement, where only two of the four Bell-basis states could be measured.
When the number of qubit in a sequence reduces to 1, the MDI-QSDC protocol
reduces to a deterministic MDI quantum key distribution protocol, which is also
presented in the Letter.
