High-capacity quantum secure direct communication with two-photon six-qubit hyperentangled states

• Published in: Science China. Physics, mechanics & astronomy mechanics & astronomy, 2017-12, Vol.60 (12), p.19-25, Article 120313
• Main Authors: Wu, FangZhou, Yang, GuoJian, Wang, HaiBo, Xiong, Jun, Alzahrani, Faris, Hobiny, Aatef, Deng, FuGuo
• Format: Article
• Language: English
• Subjects: Astronomy; Barium; BBO crystals; Classical and Continuum Physics; Communication; Observations and Techniques; Photons; Physics; Physics and Astronomy; Protocol; Qubits (quantum computing); Slabs; 双光子; 比特; 秘密信息; 纠缠态; 通信协议; 量子安全直接通信; 量子通信; 高容量
• ISSN: 1674-7348; 1869-1927
• DOI: 10.1007/s11433-017-9100-9

This study proposes the first high-capacity quantum secure direct communication（QSDC） with two-photon six-qubit hyperentangled Bell states in two longitudinal momentum and polarization degrees of freedom（DOFs） of photon pairs, which can be generated using two 0.5 mm-thick type-I β barium borate crystal slabs aligned one behind the other and an eight-hole screen. The secret message can be independently encoded on the photon pairs with 64 unitary operations in all three DOFs. This protocol has a higher capacity than previous QSDC protocols because each photon pair can carry 6 bits of information, not just 2 or 4 bits.Our QSDC protocol decreases the influence of decoherence from environment noise by exploiting the decoy photons to check the security of the transmission of the first photon sequence. Compared with two-way QSDC protocols, our QSDC protocol is immune to an attack by an eavesdropper using Trojan horse attack strategies because it is a one-way quantum communication.The QSDC protocol has good applications in the future quantum communication because of all these features.