Measurement-device-independent three-party quantum secure direct communication.

Quantum secure direct communication (QSDC) can directly transmit secure messages through quantum channel without sharing keys. Three-party (3P) QSDC enables two communication parties synchronously transmit secret messages to a third party through the quantum channels. Previous 3P-QSDC protocols all require ideal and trusted measurement devices, which are hard to realize under current experimental condition. Practical imperfect measurement devices would bring security loophole in the 3P-QSDC. In the paper, we propose a measurement-device-independent (MDI) 3P-QSDC protocol based on the polarization-spatial-mode hyperentanglement, which can resist all possible attacks from practical imperfect measurement devices. Our protocol is unconditionally secure in theory and can enhance 3P-QSDC’s security under practical experimental condition. In one round of communication, two parties can each send 2 bits of secure messages to the third party. Our MDI-3P-QSDC protocol has application potential in future multipartite quantum communication field. [ABSTRACT FROM AUTHOR]