Hefei National Research Center for Physical Sciences at the Microscale and School of Physical Sciences, University of Science and Technology of China, Hefei, China.
Shanghai Research Center for Quantum Science and CAS Center for Excellence in Quantum Information and Quantum Physics, University of Science and Technology of China, Shanghai, China.
Nature. 2023 Jul;619(7971):738-742. doi: 10.1038/s41586-023-06195-1. Epub 2023 Jul 12.
Scalable generation of genuine multipartite entanglement with an increasing number of qubits is important for both fundamental interest and practical use in quantum-information technologies. On the one hand, multipartite entanglement shows a strong contradiction between the prediction of quantum mechanics and local realization and can be used for the study of quantum-to-classical transition. On the other hand, realizing large-scale entanglement is a benchmark for the quality and controllability of the quantum system and is essential for realizing universal quantum computing. However, scalable generation of genuine multipartite entanglement on a state-of-the-art quantum device can be challenging, requiring accurate quantum gates and efficient verification protocols. Here we show a scalable approach for preparing and verifying intermediate-scale genuine entanglement on a 66-qubit superconducting quantum processor. We used high-fidelity parallel quantum gates and optimized the fidelitites of parallel single- and two-qubit gates to be 99.91% and 99.05%, respectively. With efficient randomized fidelity estimation, we realized 51-qubit one-dimensional and 30-qubit two-dimensional cluster states and achieved fidelities of 0.637 ± 0.030 and 0.671 ± 0.006, respectively. On the basis of high-fidelity cluster states, we further show a proof-of-principle realization of measurement-based variational quantum eigensolver for perturbed planar codes. Our work provides a feasible approach for preparing and verifying entanglement with a few hundred qubits, enabling medium-scale quantum computing with superconducting quantum systems.
可扩展的多体纠缠态产生对于量子信息技术的基础研究和实际应用都非常重要。一方面，多体纠缠态展示了量子力学的预测与局部实现之间的强烈矛盾，可用于研究量子到经典的转变。另一方面，实现大规模纠缠态是量子系统质量和可控性的基准，对于实现通用量子计算至关重要。然而，在最先进的量子设备上实现可扩展的多体纠缠态可能具有挑战性，需要精确的量子门和高效的验证协议。在这里，我们展示了一种在 66 量子比特超导量子处理器上制备和验证中等规模的真纠缠态的可扩展方法。我们使用了高保真度的并行量子门，并将并行单量子比特和双量子比特门的保真度优化到 99.91%和 99.05%。通过高效的随机化保真度估计，我们实现了 51 量子比特一维和 30 量子比特二维簇态，保真度分别达到 0.637±0.030 和 0.671±0.006。基于高保真度的簇态，我们进一步展示了基于测量的变分量子本征求解器用于受扰平面码的原理验证。我们的工作为制备和验证几百个量子比特的纠缠态提供了一种可行的方法，为超导量子系统实现中等规模的量子计算提供了可能。
