Quantum Information Processing
Measurement-device-independent quantum secure direct communication based on decoy states and polarization–spatial hyperentanglement
Huayao Zhang, Ri‐Gui Zhou
Abstract
Abstract Quantum secure direct communication (QSDC) can directly transmit confidential messages without pre-distributing secret keys. In practical applications, non-ideal light sources naturally contain multiphoton components, which can easily lead to photon-number-splitting attacks and constitute a core problem restricting secure practical implementation. Existing measurement-device-independent (MDI) QSDC protocols are mostly based on ideal source assumptions and lack strict security authentication for practical multiphoton risks. This paper proposes an MDI-QSDC protocol based on decoy states and polarization--spatial hyperentanglement. The protocol lower-bounds the contribution of the two-single-pair sector through an active three-intensity decoy-state mechanism and imposes a conservative bound on the potential information leakage caused by multiphoton events, while using polarization--spatial hyperentangled encoding to increase the payload of each valid HBSA event and relying on the MDI architecture to remove the need to trust the measurement device. Compared with similar schemes, this protocol significantly improves the secure message capacity in practical scenarios while maintaining detector-side security.