Quantum secure direct communication (QSDC) is an important quantum communication mode, which can directly transmit secret messages through quantum channel without the need for keys. The quantum secure direct communication with hybrid entanglement (HE-QSDC) protocol was proposed. This protocol integrates the both continuous variables (CV) and discrete variables (DV) encoding, providing an alternative approach to realize secure communication. The authors provide the complete security analysis, based on the wiretap channel theory and the Gram matrix method. This HE-QSDC protocol has two advantages. First, it employs nearly-deterministic Bell-state measurement (BSM) composed of coherent state and polarized mode in linear optics, which makes the protocol have a higher communication efficiency. Second, comparing with the protocol only using CV entanglement, this protocol has higher fidelity when satisfying the large required for near-deterministic BSM. These advantages make HE-QSDC protocol have great application potential in the field of secure communication. For more details, please refer to the article entitled “Quantum secure direct communication with hybrid entanglement” by Peng Zhao, Wei Zhong, Ming-Ming Du, Xi-Yun Li, Lan Zhou, and Yu-Bo Sheng [Front. Phys. 19(5), 51201 (2024)]. [Photo credits: Peng Zhao & Yu-Bo Sheng at Nanjing University of Posts and Telecommunications]
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