Rapid and unconditional parametric reset protocol for tunable superconducting qubits

Qubit initialization is a critical task in quantum computation and communication. Extensive efforts have been made to achieve this with high speed, efficiency and scalability. However, previous approaches have either been measurement-based and required fast feedback, suffered from crosstalk or required sophisticated calibration. Here, we report a fast and high-fidelity reset scheme, avoiding the issues above without any additional chip architecture. By modulating the flux through a transmon qubit, we realize a swap between the qubit and its readout resonator that suppresses the excited state population to 0.08% ± 0.08% within 34 ns (284 ns if photon depletion of the resonator is required). Furthermore, our approach (i) can achieve effective second excited state depletion, (ii) has negligible effects on neighboring qubits, and (iii) offers a way to entangle the qubit with an itinerant single photon, useful in quantum communication applications.

Yu Zhou, Zhenxing Zhang, Zelong Yin, Sainan Huai, Xiu Gu, Xiong Xu, Jonathan Allcock, Fuming Liu, Guanglei Xi, Qiaonian Yu, Hualiang Zhang, Mengyu Zhang, Hekang Li, Xiaohui Song, Zhan Wang, Dongning Zheng, Shuoming An, Yarui Zheng, Shengyu Zhang