  Quantum secure direct communication (QSDC) is a quantum communication
paradigm that transmits confidential messages directly using quantum states.
Measurement-device-independent (MDI) QSDC protocols can eliminate the security
loopholes associated with measurement devices. To enhance the practicality and
performance of MDI-QSDC protocols, we propose a one-photon-interference MDI
QSDC (OPI-QSDC) protocol which transcends the need for quantum memory, ideal
single-photon sources, or entangled light sources. The security of our OPI-QSDC
protocol has also been analyzed using quantum wiretap channel theory.
Furthermore, our protocol could double the distance of usual
prepare-and-measure protocols, since quantum states sending from adjacent nodes
are connected with single-photon interference, which demonstrates its potential
to extend the communication distance for point-to-point QSDC.
