提出无奇点的量子态制备方法,适配复杂噪声环境。
Singularity-free dynamical invariants-based quantum control
- 通过SU(2)子空间映射,将多体控制转为单比特问题。
- 在多种噪声下实现高保真度量子态制备,脉冲平滑可用。
- 支持已知与未知噪声,适合当前量子硬件实际需求。
量子态制备是量子技术的核心,尤其在非马尔可夫开放系统中,环境记忆和模型不确定性带来巨大挑战。基于不变量的逆向工程虽能生成解析控制场,但现有参数化常导致实验不可行的奇异脉冲,且仅限于林德布拉德型噪声模型。本文提出一种广义不变量协议,适用于任意噪声条件下的有限维系统。通过将动力学限制在设计的SU(2)子空间,将多体控制问题转化为等效单量子比特问题。控制分两步:首先构造一族在闭系统中实现完美态制备的有界脉冲;其次筛选出对噪声影响最小的最优脉冲。该框架兼容(i)已知噪声,实现噪声感知控制合成;(ii)未知噪声,无需主方程描述仍保持鲁棒性。数值模拟显示,在多种目标态下均实现高保真度制备,且生成脉冲平滑、硬件可行。该无奇点框架将不变量控制扩展至真实开放系统场景,为当前NISQ硬件及其他具非马尔可夫动力学平台提供了一条稳健的量子态工程路径。
原文摘要 · Abstract (English)
State preparation is a cornerstone of quantum technologies, underpinning applications in computation, communication, and sensing. Its importance becomes even more pronounced in non-Markovian open quantum systems, where environmental memory and model uncertainties pose significant challenges to achieving high-fidelity control. Invariant-based inverse engineering provides a principled framework for synthesizing analytic control fields, yet existing parameterizations often lead to experimentally infeasible, singular pulses and are limited to simplified noise models such as those of Lindblad form. Here, we introduce a generalized invariant-based protocol for finite-dimensional state preparation under arbitrary noise conditions. We transform the finite-dimensional control problem into the equivalent problem for a single-qubit, by restricting the dynamics to a designed SU(2) subspace. The control protocol then proceeds in two-stages: first, we construct a family of bounded pulses that achieve perfect state preparation in a closed system; second, we identify the optimal member of this family that minimizes the effect of noise. The framework accommodates both (i) characterized noise, enabling noise-aware control synthesis, and (ii) uncharacterized noise, where a noise-agnostic variant preserves robustness without requiring a master-equation description. Numerical simulations demonstrate high-fidelity state preparation across diverse targets while producing smooth, hardware-feasible control fields. This singularity-free framework extends invariant-based control to realistic open-system regimes, providing a versatile route toward robust quantum state engineering on NISQ hardware and other platforms exhibiting non-Markovian dynamics.
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