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arXiv 2307.03310quant-phcond-mat.mes-hall
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通过机器学习寻找可积量子多体系统的动力学

Finding the Dynamics of an Integrable Quantum Many-Body System via Machine Learning

Victor Wei, Alev Orfi, Felix Fehse, W. A. Coish

AI总结:

针对可积Gaudin磁体动力学缺乏通用闭式解析解的问题,研究采用受限玻尔兹曼机结合变分蒙特卡罗方法得到其低能本征态,进而求得非微扰动力学横向自旋磁化率,为相关量子比特的表征与控制提供支撑。

摘要:

我们采用机器学习方法研究Gaudin磁体(“中心自旋模型”)的动力学。该模型具有实际应用价值,例如可用于研究与大环境自旋库相互作用的中心自旋的非马尔可夫退相干动力学,以及非平衡超导性研究。Gaudin磁体同时也是可积系统,存在大量守恒量:对于$N$个自旋的情形,模型哈密顿量可写为$N$个独立对易算符之和。尽管具备如此高的对称性,该多体问题动力学的通用闭式解析解仍未找到。机器学习方法或许非常适合利用可积问题中的高度对称性,即便显式解析解并不明确。部分受这一思路启发,我们为模型哈密顿量的每个变分本征态采用了神经网络表示(受限玻尔兹曼机,restricted Boltzmann machine)。随后通过变分蒙特卡罗计算,我们得到了Gaudin磁体哈密顿量基态与低激发态的精确表示。基于这些低能本征态,我们求得了非微扰的动力学横向自旋磁化率,该物理量描述了存在自旋库时中心自旋对时变横向磁场的线性响应。获得这种磁化率的高效描述,为改进与量子二能级系统环境相互作用的量子比特的表征与量子控制流程开辟了道路。这类系统包括通过超精细相互作用与环境核自旋相互作用的电子自旋和空穴自旋量子比特,或是具有电荷或通量自由度、与相干电荷或顺磁杂质相互作用的量子比特。

英文摘要:

We study the dynamics of the Gaudin magnet ("central-spin model") using machine-learning methods. This model is of practical importance, e.g., for studying non-Markovian decoherence dynamics of a central spin interacting with a large bath of environmental spins and for studies of nonequilibrium superconductivity. The Gaudin magnet is also integrable, admitting many conserved quantities: For $N$ spins, the model Hamiltonian can be written as the sum of $N$ independent commuting operators. Despite this high degree of symmetry, a general closed-form analytic solution for the dynamics of this many-body problem remains elusive. Machine-learning methods may be well suited to exploiting the high degree of symmetry in integrable problems, even when an explicit analytic solution is not obvious. Motivated in part by this intuition, we use a neural-network representation (restricted Boltzmann machine) for each variational eigenstate of the model Hamiltonian. We then obtain accurate representations of the ground state and of the low-lying excited states of the Gaudin-magnet Hamiltonian through a variational Monte Carlo calculation. From the low-lying eigenstates, we find the non-perturbative dynamic transverse spin susceptibility, describing the linear response of a central spin to a time-varying transverse magnetic field in the presence of a spin bath. Having an efficient description of this susceptibility opens the door to improved characterization and quantum control procedures for qubits interacting with an environment of quantum two-level systems. These systems include electron-spin and hole-spin qubits interacting with environmental nuclear spins via hyperfine interactions or qubits with charge or flux degrees of freedom interacting with coherent charge or paramagnetic impurities.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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