Flux qubit in a dc SQUID with the 4π period Josephson effect Wen-Chao Huang, Qi-Feng Liang, Dao-Xin Yao and Zhi Wang EPL, 110 3 (2015) 37010 Published online: 25 May 2015 DOI: 10.1209/0295-5075/110/37010