Ni Zhongchu, Li Sai, Zhang Libo, Chu Ji, Niu Jingjing, Yan Tongxing, Deng Xiuhao, Hu Ling, Li Jian, Zhong Youpeng, Liu Song, Yan Fei, Xu Yuan, Yu Dapeng
Shenzhen Institute for Quantum Science and Engineering, Southern University of Science and Technology, Shenzhen 518055, China.
International Quantum Academy, Shenzhen 518048, China.
Phys Rev Lett. 2022 Jul 22;129(4):040502. doi: 10.1103/PhysRevLett.129.040502.
Unwanted ZZ interaction is a quantum-mechanical crosstalk phenomenon which correlates qubit dynamics and is ubiquitous in superconducting qubit systems. It adversely affects the quality of quantum operations and can be detrimental in scalable quantum information processing. Here we propose and experimentally demonstrate a practically extensible approach for complete cancellation of residual ZZ interaction between fixed-frequency transmon qubits, which are known for long coherence and simple control. We apply to the intermediate coupler that connects the qubits a weak microwave drive at a properly chosen frequency in order to noninvasively induce an ac Stark shift for ZZ cancellation. We verify the cancellation performance by measuring vanishing two-qubit entangling phases and ZZ correlations. In addition, we implement a randomized benchmarking experiment to extract the idling gate fidelity which shows good agreement with the coherence limit, demonstrating the effectiveness of ZZ cancellation. Our method allows independent addressability of each qubit-qubit connection and is applicable to both nontunable and tunable couplers, promising better compatibility with future large-scale quantum processors.
不需要的ZZ相互作用是一种量子力学串扰现象，它与量子比特动力学相关，并且在超导量子比特系统中普遍存在。它会对量子操作的质量产生不利影响，并且在可扩展量子信息处理中可能是有害的。在此，我们提出并通过实验证明了一种切实可行的可扩展方法，用于完全消除固定频率transmon量子比特之间的残余ZZ相互作用，这些量子比特以长相干性和简单控制而闻名。我们在连接量子比特的中间耦合器上施加一个频率适当的弱微波驱动，以便非侵入性地诱导交流斯塔克位移以消除ZZ相互作用。我们通过测量消失的双量子比特纠缠相位和ZZ相关性来验证消除性能。此外，我们进行了一次随机基准测试实验，以提取空闲门保真度，该保真度与相干极限显示出良好的一致性，证明了ZZ消除的有效性。我们的方法允许对每个量子比特-量子比特连接进行独立寻址，并且适用于不可调谐和可调谐耦合器，有望与未来的大规模量子处理器具有更好的兼容性。
