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arXiv 1408.3100quant-phcs.AImath.STstat.TH
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密度矩阵的贝叶斯概率计算

A Bayesian Probability Calculus for Density Matrices

University of California, Santa Cruz(加州大学圣克鲁兹分校)

Manfred K. Warmuth, Dima Kuzmin

摘要:

密度矩阵是量子物理中的一个重要概念,它是迹1的对称正定矩阵。有限概率分布是密度矩阵被限制为对角的特殊情况。密度矩阵是二元矩阵的混合,其中二元矩阵对于任何单位列向量u具有形式uu'。这些单位向量是广义概率空间的基本事件。也许最简单的情况下,看到一些不寻常的事情正在进行的情况下,均匀密度矩阵,即1/n倍的身份。这个矩阵将概率1/n分配给每个单位向量,但当然有无穷多个单位向量。因此,新的归一化规则表明,在任何方向的正交基上的概率之和是1。我们开发了一个概率演算的基础上,这些更一般的分布,其中包括关节,条件和公式的定义,这些相关的,即类似物的定理的总概率,各种贝叶斯规则的计算后密度矩阵等所产生的演算平行熟悉的“经典”概率演算,并始终保留后者作为一个特殊情况下,当所有的矩阵是对角的。而经典的贝叶斯方法保持不确定性的模型是“最好的”,泛化保持不确定性的单位方向具有最大的方差。令人惊讶的是,边界也概括:在经典的设置,我们绑定的负对数似然数据的负对数似然的MAP估计。

英文摘要:

One of the main concepts in quantum physics is a density matrix, which is a symmetric positive definite matrix of trace one. Finite probability distributions are a special case where the density matrix is restricted to be diagonal. Density matrices are mixtures of dyads, where a dyad has the form uu' for any any unit column vector u. These unit vectors are the elementary events of the generalized probability space. Perhaps the simplest case to see that something unusual is going on is the case of uniform density matrix, i.e. 1/n times identity. This matrix assigns probability 1/n to every unit vector, but of course there are infinitely many of them. The new normalization rule thus says that sum of probabilities over any orthonormal basis of directions is one. We develop a probability calculus based on these more general distributions that includes definitions of joints, conditionals and formulas that relate these, i.e. analogs of the theorem of total probability, various Bayes rules for the calculation of posterior density matrices, etc. The resulting calculus parallels the familiar 'classical' probability calculus and always retains the latter as a special case when all matrices are diagonal. Whereas the classical Bayesian methods maintain uncertainty about which model is 'best', the generalization maintains uncertainty about which unit direction has the largest variance. Surprisingly the bounds also generalize: as in the classical setting we bound the negative log likelihood of the data by the negative log likelihood of the MAP estimator.

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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