近日，美国哈佛大学的Mikhail D. Lukin及其研究团队取得一项新进展。经过不懈努力，他们实现基于可重构原子阵列的逻辑量子处理器。相关研究成果已于2023年12月6日在国际权威学术期刊《自然》上发表。

该研究团队报道了一种基于编码逻辑量子比特的可编程量子处理器的实现，最多可运行280个物理量子比特。利用逻辑级控制和可重构中性原子阵列中的分区架构，该研究的系统结合了高双量子比特门保真度、任意连接以及完全可编程的单量子比特旋转和中间电路读出。通过使用不同类型的编码操作该逻辑处理器，研究人员演示了通过将表面编码距离从d=3缩放到d=7，制备收支平衡保真度的色码量子比特、逻辑GHZ态的容错创建和前馈纠缠隐形传态以及操作40个色码量子比特来改进双量子比特逻辑门。

最后，通过使用三维[[8,3,2]]代码块，研究人员实现了具有多达48个逻辑量子比特的计算复杂采样电路，该电路与228个逻辑双量子比特门和48个逻辑CCZ门的超立方体连接纠缠在一起。研究人员发现这种逻辑编码通过误差检测大大提高了算法性能，在交叉熵基准测试和快速置乱的量子模拟中都优于物理量子比特保真度。这些结果预示着早期纠错量子计算的到来，并为大规模逻辑处理器的发展指明了道路。

据悉，抑制误差是有用量子计算的核心挑战，需要大规模处理的量子误差校正。然而，在实现纠错的“逻辑”量子比特时，信息需要在许多物理量子比特上进行编码以实现冗余，这给大规模逻辑量子计算带来了重大挑战。

附：英文原文

Title: Logical quantum processor based on reconfigurable atom arrays

Author: Bluvstein, Dolev, Evered, Simon J., Geim, Alexandra A., Li, Sophie H., Zhou, Hengyun, Manovitz, Tom, Ebadi, Sepehr, Cain, Madelyn, Kalinowski, Marcin, Hangleiter, Dominik, Ataides, J. Pablo Bonilla, Maskara, Nishad, Cong, Iris, Gao, Xun, Rodriguez, Pedro Sales, Karolyshyn, Thomas, Semeghini, Giulia, Gullans, Michael J., Greiner, Markus, Vuleti, Vladan, Lukin, Mikhail D.

Issue&Volume: 2023-12-06

Abstract: Suppressing errors is the central challenge for useful quantum computing, requiring quantum error correction for large-scale processing. However, the overhead in the realization of error-corrected “logical” qubits, where information is encoded across many physical qubits for redundancy, poses significant challenges to large-scale logical quantum computing. Here we report the realization of a programmable quantum processor based on encoded logical qubits operating with up to 280 physical qubits. Utilizing logical-level control and a zoned architecture in reconfigurable neutral atom arrays, our system combines high two-qubit gate fidelities, arbitrary connectivity, as well as fully programmable single-qubit rotations and mid-circuit readout. Operating this logical processor with various types of encodings, we demonstrate improvement of a two-qubit logic gate by scaling surface code distance from d=3 to d=7, preparation of color code qubits with break-even fidelities, fault-tolerant creation of logical GHZ states and feedforward entanglement teleportation, as well as operation of 40 color code qubits. Finally, using three-dimensional [[8,3,2]] code blocks, we realize computationally complex sampling circuits with up to 48 logical qubits entangled with hypercube connectivity with 228 logical two-qubit gates and 48 logical CCZ gates. We find that this logical encoding substantially improves algorithmic performance with error detection, outperforming physical qubit fidelities at both cross-entropy benchmarking and quantum simulations of fast scrambling. These results herald the advent of early error-corrected quantum computation and chart a path toward large-scale logical processors.

DOI: 10.1038/s41586-023-06927-3

Source: https://www.nature.com/articles/s41586-023-06927-3