Fast qubit initialization in a superconducting circuit* *Project supported by the National Key R&D Program of China (Grant No. 2016YFA0301802), the National Natural Science Foundation of China (Grant Nos. 61521001, 11474153, and 11890704), and the Key R/D Program of Guangdong Province, China (Grant No. 2018B030326001).

Abstract

We demonstrate an active reset protocol in a superconducting quantum circuit. The thermal population on the excited state of a transmon qubit is reduced through driving the transitions between the qubit and an ancillary qubit. Furthermore, we investigate the efficiency of this approach at different temperatures. The result shows that population in the first excited state can be dropped from 7% to 2.55% in 27 ns at 30 mK. The efficiency improves as the temperature increases. Compared to other schemes, our proposal alleviates the requirements for measurement procedure and equipment. With the increase of qubit integration, the fast reset technique holds the promise of improving the fidelity of quantum control.