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arXiv 1709.01985quant-ph
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Majorana费米子的相空间方法

Phase space methods for Majorana fermions

Ria Rushin Joseph, Laura E. C. Rosales-Zárate, Peter D. Drummond

摘要:

费米子相空间表象是研究关联费米子系统的一种很有前途的方法。利用费米子湮灭算符和产生算符的高斯算符定义了费米子Q函数和P函数。协方差矩阵的相空间属于对称类D,非标准对称类之一。这最初是为了研究介观正常金属-超导混合结构而提出的,这种结构导致了最近对马约拉纳费米子的实验观察。在酉变换下,可以用实反对称矩阵和马约拉纳算子来表示这些高斯算子,它们是更简单的数学对象。我们推导出涉及Majorana费米子算子和一个反对称矩阵的微分恒等式,这与对称空间上相应的Fokker-Planck方程的推导有关。这些使随机模拟无论是在真实的或虚构的时间。这种形式主义有直接的关系,其中有马约拉纳型激发的费米子系统的研究,是一种替代使用涉及传统的费米运营商的扩展。该方法示出了如何线性耦合哈密顿用于研究拓扑激发可以转化为福克-普朗克和随机方程的形式,包括通过粒子损耗耗散。

英文摘要:

Fermionic phase space representations are a promising method for studying correlated fermion systems. The fermionic Q-function and P-function have been defined using Gaussian operators of fermion annihilation and creation operators. The resulting phase-space of covariance matrices belongs to the symmetry class D, one of the non-standard symmetry classes. This was originally proposed to study mesoscopic normal-metal-superconducting hybrid structures, which is the type of structure that has led to recent experimental observations of Majorana fermions. Under a unitary transformation, it is possible to express these Gaussian operators using real anti-symmetric matrices and Majorana operators, which are much simpler mathematical objects. We derive differential identities involving Majorana fermion operators and an antisymmetric matrix which are relevant to the derivation of the corresponding Fokker-Planck equations on symmetric space. These enable stochastic simulations either in real or imaginary time. This formalism has direct relevance to the study of fermionic systems in which there are Majorana type excitations, and is an alternative to using expansions involving conventional Fermi operators. The approach is illustrated by showing how a linear coupled Hamiltonian as used to study topological excitations can be transformed to Fokker-Planck and stochastic equation form, including dissipation through particle losses.

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