Proof-of-principle demonstration of semi-quantum key distribution based on the Mirror protocol Siyu Han, Yutao Huang, Shang Mi, Xiaojuan Qin, Jindong Wang, Yafei Yu, Zhengjun Wei and Zhiming Zhang EPJ Quantum Technol., 8 1 (2021) 28 Published online: 20 December 2021 DOI: 10.1140/epjqt/s40507-021-00117-8