近日，美国IBM量子公司的Edward H. Chen与德国科隆大学的Guo-Yi Zhu等人合作并取得一项新进展。经过不懈努力，他们揭示跨越恒定深度量子电路错误阈值的西森跃迁。相关研究成果已于2024年12月16日在国际知名学术期刊《自然—物理学》上发表。

该研究团队展示了在存在相干和非相干误差的情况下，使用基于测量的协议在54个系统量子比特上生成最简单的长程序——伊辛序。研究人员实现了一个恒定深度的制备协议，该协议利用对测量的经典解码来识别长程序，而这种长程序通常会被量子测量的随机性所掩盖。

通过实验调整错误率，研究人员在二维空间中展示了这种解码后的长程序的稳定性，直至达到属于不寻常的西森普适类的临界相变点。尽管在经典系统中，西森物理需要精细调整多个参数，但在本研究中，它是测量概率的玻恩规则的直接结果。这项研究展示了在超过一百个量子比特的量子处理器上可以探索的涌现现象。

据悉，量子计算涉及在多量子比特之间制备纠缠态。这需要高效且对噪声和门不完美性具有稳定性的制备协议。

附：英文原文

Title: Nishimori transition across the error threshold for constant-depth quantum circuits

Author: Chen, Edward H., Zhu, Guo-Yi, Verresen, Ruben, Seif, Alireza, Bumer, Elisa, Layden, David, Tantivasadakarn, Nathanan, Zhu, Guanyu, Sheldon, Sarah, Vishwanath, Ashvin, Trebst, Simon, Kandala, Abhinav

Issue&Volume: 2024-12-16

Abstract: Quantum computing involves the preparation of entangled states across many qubits. This requires efficient preparation protocols that are stable to noise and gate imperfections. Here we demonstrate the generation of the simplest long-range order—Ising order—using a measurement-based protocol on 54 system qubits in the presence of coherent and incoherent errors. We implement a constant-depth preparation protocol that uses classical decoding of measurements to identify long-range order that is otherwise hidden by the randomness of quantum measurements. By experimentally tuning the error rates, we demonstrate the stability of this decoded long-range order in two spatial dimensions, up to a critical phase transition belonging to the unusual Nishimori universality class. Although in classical systems Nishimori physics requires fine-tuning multiple parameters, here it arises as a direct result of the Born rule for measurement probabilities. Our study demonstrates the emergent phenomena that can be explored on quantum processors beyond a hundred qubits.

DOI: 10.1038/s41567-024-02696-6

Source: https://www.nature.com/articles/s41567-024-02696-6