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arXiv 2209.07355quant-phcond-mat.str-el
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具有非反常矩阵乘积算符对称性的量子态的测量

Gauging quantum states with non-anomalous matrix product operator symmetries

José Garre Rubio, Ilya Kull

摘要:

测量系统的全局对称性等于引入新的自由度,其变换规则使整个系统观察到局部对称性。在量子系统中,测量全局对称性可能会遇到障碍。当这种情况发生时,对称性被称为反常。这样的障碍与全局对称性不能写成局部算子的张量积的事实有关。在这份手稿中,我们研究非局部对称性,有一个额外的结构:他们采取的形式矩阵产品运营商(MPO)。我们利用张量网络结构的MPO构建本地运营商从他们满足相同的组关系,也就是说,我们能够本地化甚至异常MPO。对于非反常的MPO,我们使用这些局域算符来明确地规范一维量子态的MPO对称性,从而得到非平凡的规范态。我们表明,我们的测量程序满足所有所需的属性作为标准的现场情况下。我们还展示了这个过程是如何自然地表示在矩阵产品的MPO对称性保护的状态。在异常MPO的情况下,我们揭示了测量这些对称性的障碍。

英文摘要:

Gauging a global symmetry of a system amounts to introducing new degrees of freedom whose transformation rule makes the overall system observe a local symmetry. In quantum systems there can be obstructions to gauging a global symmetry. When this happens the symmetry is dubbed anomalous. Such obstructions are related to the fact that the global symmetry cannot be written as a tensor product of local operators. In this manuscript we study non-local symmetries that have an additional structure: they take the form of a matrix product operator (MPO). We exploit the tensor network structure of the MPOs to construct local operators from them satisfying the same group relations, that is, we are able to localize even anomalous MPOs. For non-anomalous MPOs, we use these local operators to explicitly gauge the MPO symmetry of a one-dimensional quantum state obtaining non-trivial gauged states. We show that our gauging procedure satisfies all the desired properties as the standard on-site case does. We also show how this procedure is naturally represented in matrix product states protected by MPO symmetries. In the case of anomalous MPOs, we shed light on the obstructions to gauging these symmetries.

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