A novel semiquantum key distribution protocol with Bell states

In this paper, a novel semiquantum key distribution (SQKD) protocol is proposed using Bell states, where quantum Alice can share secret bits with semiquantum Bob via a quantum channel. Semiquantum Bob is required to measure particles with the basis (i.e. ), produce fresh particles within the basis and send particles via a quantum channel. Security analysis turns out that this protocol is immune to various attacks launched by the outside eavesdropper. Compared with present SQKD protocols using Bell states without a third party (Sun et al 2011 arXiv:1106.2910v3; Wang et al 2011 Chin. Phys. Lett.28 100301; Wu et al 2022 Front. Phys. 10 1029262), on the one hand, this protocol has the highest qubit efficiency; and, on the other hand, the reflecting operations of the semiquantum user in this protocol contribute to the generation of final shared keys.