Superconducting quantum bits<xref rid="cpb_27_2_027401fn1" ref-type="fn">*</xref> <fn id="cpb_27_2_027401fn1"> <label>*</label> <p>Project supported by the National Natural Science Foundation of China (Grant Nos. 91321208 and 11674380) and the National Key Basic Research Program of the Ministry of Science and Technology of China (Grant Nos. 2014CB921202, 2015CB921104, and 2016YFA0300601).</p> </fn>

Superconducting quantum bits* *

Project supported by the National Natural Science Foundation of China (Grant Nos. 91321208 and 11674380) and the National Key Basic Research Program of the Ministry of Science and Technology of China (Grant Nos. 2014CB921202, 2015CB921104, and 2016YFA0300601).

Liu Wei-Yang^{1, 2}, Zheng Dong-Ning^{1, 2}, Zhao Shi-Ping^{1, 2, †}

(color online) (a) A persistent-current flux qubit schematic. (b) A contour plot of the potential in Eq. (8). (c) The potential along the direction indicated by a red line in panel (b) when Φ_e ≠ Φ₀/2. States in the two potential wells correspond to the currents circulating in the qubit loop with opposite polarities.