近日，美国马里兰大学的Michael J. Gullans等取得一项新进展。经过不懈努力，他们揭示了随机量子电路中魔法的相变现象。相关研究成果已于2024年9月23日在国际知名学生期刊《自然—物理学》上发表。

该研究团队观察到，在相干误差的影响下，随机稳定器码会表现出魔法的相变，研究人员通过解析、数值和实验探测对其进行了表征。在低于临界错误率的条件下，稳定器测量会消除电路中累积的魔法，从而有效抵御相干误差；而在高于临界错误率的条件下，测量则会集中魔法。在魔法的资源理论中更好地理解这一行为，有助于识别量子加速的来源，并导出更高效生成魔法态的方法。

据悉，魔法是量子态的一种属性，它使得仅使用简单的门操作集便能实现通用的容错量子计算。因此，理解魔法产生或消失的机制是实现高效且实用的容错计算的关键一步。量子计算中的许多纠错方案都采用了所谓的稳定器码，这些码通过多量子比特测量来检测逻辑量子比特状态的偏差。

附：英文原文

Title: Phase transition in magic with random quantum circuits

Author: Niroula, Pradeep, White, Christopher David, Wang, Qingfeng, Johri, Sonika, Zhu, Daiwei, Monroe, Christopher, Noel, Crystal, Gullans, Michael J.

Issue&Volume: 2024-09-23

Abstract: Magic is a property of quantum states that enables universal fault-tolerant quantum computing using simple sets of gate operations. Understanding the mechanisms by which magic is created or destroyed is, therefore, a crucial step towards efficient and practical fault-tolerant computation. Many proposals for error correction in quantum computing make use of so-called stabilizer codes, which use multiqubit measurements to detect deviations from logical qubit states. Here we observe that a random stabilizer code subject to coherent errors exhibits a phase transition in magic, which we characterize through analytical, numerical and experimental probes. Below a critical error rate, stabilizer measurements remove the accumulated magic in the circuit, effectively protecting against coherent errors; above the critical error rate measurements concentrate magic. A better understanding of this behaviour in the resource theory of magic could help to identify the origins of quantum speedup and lead to methods for more efficient magic state generation.

DOI: 10.1038/s41567-024-02637-3

Source: https://www.nature.com/articles/s41567-024-02637-3