论文标题
带Python的PYMC的贝叶斯量子层析成像
Bayesian Quantum State Tomography with Python's PyMC
论文作者
论文摘要
量子状态层析成像(QST)通常是使用最大似然估计(MLE)从频繁的观点中进行的,该估计值(MLE)试图通过最大程度地提高可能性函数 /分布来找到与数据一致的最佳合理状态。可能性函数有一个隐含的假设,即有适当的数据可以推断频率。在数据耗尽的实验中,这可能是一个可行的假设。此外,MLE返回最终解决方案的错误估计,并且用户被迫依靠涉及其他测量或模拟数据的替代方法。另外,贝叶斯方法可以返回具有与数据不确定性一致的错误估计的解决方案,但以可能在可能性分布上的困难集成为代价。集成通常需要具有适当选择的步骤大小的计算方法,以某种复杂的问题制定。尽管有优势,但这种额外的复杂性是对使用贝叶斯方法的强烈威慑力量。概率编程正在成为日益增长的计算能力以及强大的自动化整合技术(例如马尔可夫链蒙特卡洛(MCMC))的开发的常见替代方法。在这里,我们展示了如何使用Python-3的开源PYMC概率编程软件包将原本复杂的QST优化问题转换为一种简单的形式,可以通过有效的下层MCMC采样器快速优化,该形式可以快速优化。
Quantum state tomography (QST) is typically performed from a frequentist viewpoint using maximum likelihood estimation (MLE) which seeks to find the best plausible state consistent with the data by maximizing a likelihood function / distribution. The likelihood function holds an implicit assumption that there is suitable data to infer frequency. In data-starved experiments, this may or may not be a feasible assumption. Moreover, MLE returns no error estimates on the final solution and users are forced to rely on alternative approaches involving either additional measurements or simulated data. Alternatively, Bayesian methods can return a solution with error estimates consistent with the data's uncertainty, but at the expense of a difficult integration over the likelihood distribution. The integration usually requires computational methods with appropriately chosen step sizes in a somewhat complicated problem formulation. This additional complexity serves as a strong deterrent from using Bayesian methods despite the advantages. Probabilistic programming is becoming a common alternative with growing computational power and the development of robust automated integration techniques such as Markov-Chain Monte Carlo (MCMC). Here, we show how to use Python-3's open source PyMC probabilistic programming package to transform an otherwise complicated QST optimization problem into a simple form that can be quickly optimized with efficient under-the-hood MCMC samplers.