Deng Xiang, Zheng Wen, Liao Xudong, Zhou Haoyu, Ge Yangyang, Zhao Jie, Lan Dong, Tan Xinsheng, Zhang Yu, Li Shaoxiong, Yu Yang
Nanjing University, National Laboratory of Solid State Microstructures, School of Physics, Nanjing 210093, China.
Nanjing University, Shishan Laboratory, Suzhou Campus of , Suzhou 215163, China.
Phys Rev Lett. 2025 Jan 17;134(2):020801. doi: 10.1103/PhysRevLett.134.020801.
Superconducting quantum computing emerges as one of the leading candidates for achieving quantum advantage. However, a prevailing challenge is the coding overhead due to limited quantum connectivity, constrained by nearest-neighbor coupling among superconducting qubits. Here, we propose a novel multimode coupling scheme using three resonators driven by two microwaves, based on the resonator-induced phase gate, to extend the ZZ interaction distance between qubits. We demonstrate a controlled-Z (cz) gate fidelity exceeding 99.9% within 160 ns at a free spectral range (FSR) of 1.4 GHz, and by optimizing driving pulses, we further reduce the residual photon to nearly 10^{-3} within 100 ns at a FSR of 0.2 GHz. These facilitate the long-range cz gate over separations reaching submeters, thus significantly enhancing qubit connectivity and making a practical step toward the scalable integration and modularization of quantum processors. Specifically, our approach supports the implementation of quantum error correction codes requiring high connectivity, such as low-density parity check codes that pave the way to achieving fault-tolerant quantum computing.
超导量子计算成为实现量子优势的主要候选方案之一。然而，一个普遍存在的挑战是由于量子连接性有限导致的编码开销，这受到超导量子比特之间最近邻耦合的限制。在此，我们基于谐振器诱导相位门，提出一种使用由两个微波驱动的三个谐振器的新型多模耦合方案，以扩展量子比特之间的ZZ相互作用距离。我们在1.4GHz的自由光谱范围（FSR）内，于160ns内展示了超过99.9%的受控Z（cz）门保真度，并且通过优化驱动脉冲，在0.2GHz的FSR下，于100ns内将残余光子进一步降低至接近10^-3。这些有助于实现跨度达亚米级的远程cz门，从而显著增强量子比特连接性，并朝着量子处理器的可扩展集成和模块化迈出切实的一步。具体而言，我们的方法支持实现需要高连接性的量子纠错码，例如为实现容错量子计算铺平道路的低密度奇偶校验码。
