Two-step quantum secure direct communication scheme with frequency coding*

Project supported by the National Natural Science Foundation of China (Grant Nos. 11175094, 91221205, and 11547035) and the National Basic Research Program of China (Grant No. 2015CB921002).

Zhao Xue-Liang1, Li Jun-Lin1, Niu Peng-Hao1, Ma Hong-Yang2, Ruan Dong1, †
       

(color online) The frequency spectrum in a noisy channel with 5% error rate. The x-axis is the frequency and the y-axis is the Fourier transformed amplitude.