近日，清华大学的吴热冰及其研究小组与华为技术有限公司的Man Hong Yung等人合作并取得一项新进展。经过不懈努力，他们实现量子速度极限下单量子比特门的鲁棒控制。相关研究成果已于2024年8月5日在国际知名学术期刊《物理评论A》上发表。
在本文中，该研究团队研究了旨在实现最佳平衡的鲁棒时间最优控制问题。基于系统关于不确定性参数的泰勒展开，研究人员将设计问题表述为在量子速度极限（QSL）下对增广有限维系统的最优控制，其中鲁棒性由级数截断的顺序来分级。然后，引入梯度下降算法来顺序寻找对应于不同鲁棒性顺序的QSL。
研究人员对具有频率和场幅度不确定性的单量子比特系统进行了数值模拟，所获得的时间最优控制脉冲可以有效地将门误差抑制到规定的鲁棒性顺序。这些结果为在量子电路的脉冲级编译中选择脉冲长度提供了实用指南。
据悉，在量子计算中实现高保真度门时，快速性和鲁棒性都至关重要，但在实践中必须在它们之间做出权衡。
附：英文原文
Title: Robust control of single-qubit gates at the quantum speed limit
Author: Xi Cao, Jiangyu Cui, Man Hong Yung, Re-Bing Wu
Issue&Volume: 2024/08/05
Abstract: Fastness and robustness are both critical in the implementation of high-fidelity gates for quantum computation, but in practice a trade-off has to be made between them. In this paper, we investigate the robust time-optimal control problem that aims at the best balance. Based on the Taylor expansion of the system in terms of uncertainty parameters, we formulate the design problem as the optimal control of an augmented finite-dimensional system at its quantum speed limit (QSL), where the robustness is graded by the order of series truncation. The gradient-descent algorithm is then introduced to sequentially seek QSLs corresponding to different orders of robustness. Numerical simulations are carried out for single-qubit systems with frequency and field amplitude uncertainties, and the obtained time-optimal control pulses can effectively suppress gate errors to the prescribed robustness order. These results provide a practical guide for selecting pulse lengths in the pulse-level compilation of quantum circuits.
DOI: 10.1103/PhysRevA.110.022603
Source: https://journals.aps.org/pra/abstract/10.1103/PhysRevA.110.022603
期刊信息
Physical Review A：《物理评论A》，创刊于1970年。隶属于美国物理学会，最新IF：2.97
官方网址：https://journals.aps.org/pra/
投稿链接：https://authors.aps.org/Submissions/login/new