通过双正交分解实现快速驱动下的无耗散自由能估算
Stochastic Counterdiabatic Driving via Biorthogonal Liouvillian Eigenmodes

- 基于李普希亚算子的谱分解构造反绝热修正项
- 在任意驱动速度下抑制非绝热滞后,误差降低12个数量级
- 适合需要高精度自由能计算的分子模拟研究者
有限时间驱动随机系统会产生超额耗散,导致概率分布滞后于瞬时平衡态,进而降低基于Jarzynski等式的非平衡自由能估计器的收敛性。受控自由能模拟通过设计控制场\mathbf{u}消除这种滞后,强制实现路径上的功等于自由能变化\mathcal{W}_\mathbf{u} = Δ\mathcal{F},从而获得零方差估计。然而,闭式形式的控制场构造仍具挑战,现有方法包括流场法、靶向自由能扰动或学习微分同胚。本文提出一种基于规范变换而非广义坐标变换的数值框架,基于时变福克-普朗克生成元的精确谱分解实现完美受控。李普希亚算子的双正交分解直接导出反绝热修正项,其作用于瞬时平衡分布可完全抵消任意驱动速度下的非绝热滞后,形式上类比量子系统的速达绝热技术(如Berry的无跃迁驱动)。在过阻尼粒子在时变双阱势和谐振阱中的模拟中,数值验证表明反绝热条件满足机器精度,非绝热滞后在总变差距离上抑制约十二个数量级,在KL散度上抑制十六个数量级,相较未受控动力学。作为诊断,我们展示在所有协议速度下确定性传播的福克-普朗克密度的耗散功\mathcal{W}_{\text{diss}}(t) \approx 0。
原文摘要 · Abstract (English)
Finite-time driving of stochastic systems generates excess dissipation, causing the evolving probability distribution to lag behind the instantaneous equilibrium, and consequently degrading the convergence of nonequilibrium free energy estimators based on the Jarzynski equality. Escorted free energy simulations address the non-adiabatic lag by engineering control fields $\mathbf{u}$ that eliminate the lag, enforcing the trajectory-wise equality $\mathcal{W}_\mathbf{u} = Δ\mathcal{F}$, and yielding zero-variance estimators. However, constructing the escorting field in closed form remains a challenge, approached variously through flow-field methods, targeted free energy perturbation, or learned diffeomorphisms. In this work, we construct a complementary numerical framework based on gauge-type transforms instead of generalized coordinate transforms for perfect escorting based on the exact spectral decomposition of the time-dependent Fokker-Planck generator. The biorthogonal decomposition of the Liouville operator directly yields a counterdiabatic correction whose action on the instantaneous equilibrium distribution exactly cancels the non-adiabatic lag at arbitrary driving speed in formal analogy with shortcuts-to-adiabaticity techniques such as Berry's transitionless driving for quantum systems. Numerical verification for simulations of an overdamped particle in a time-varying double-well potential and harmonic traps confirms that the counterdiabatic condition is satisfied to machine precision, with the non-adiabatic lag suppressed by roughly twelve orders of magnitude in total variation distance and sixteen orders in KL divergence relative to the unescorted dynamics. As a diagnostic, we demonstrate vanishing dissipated work $\mathcal{W}_{\text{diss}}(t) \approx 0$ for the deterministically propagated Fokker-Planck density across all protocol speeds.
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