A Tunable Hybrid Qubit in a GaAs Double Quantum Dot

Gang Cao, Hai-Ou Li, Guo-Dong Yu, Bao-Chuan Wang, Bao-Bao Chen, Xiang-Xiang Song, Ming Xiao, Guang-Can Guo, Hong-Wen Jiang, Xue-Dong Hu, Guo-Ping Guo

Published 2015-10-04Version 1

We experimentally demonstrate a hybrid qubit in a GaAs double quantum dot. The qubit is encoded in the (1, 4) charge regime of the double dot, and can be manipulated completely electrically. The qubit has frequencies that fall conveniently within the microwave range. More importantly, a dot anharmonicity leads to quasi-parallel energy levels and a new anti-crossing, which help preserve quantum coherence of the qubit and yield a useful working point. We have performed Larmor precession and Ramsey fringe experiments near the new working point, and find that the qubit decoherence time is significantly improved over a charge qubit. This work shows a new way to encode a semiconductor logical qubit that is controllable and coherent.