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arXiv 1306.2519cond-mat.mes-hallquant-ph
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非平衡噪声对Majorana零模量子存储器的影响

Effects of non-equilibrium noise on a quantum memory encoded in Majorana zero modes

François Konschelle, Fabian Hassler

摘要:

为了提高拓扑量子存储器在具有Majorana零模的系统中的相干时间,最近有人提出将逻辑量子比特态编码为非局域Majorana算符,该算符不受涉及非成对Majorana模的局域激发的影响.在这种编码中,逻辑错误仅发生在准粒子在其激发之后行进马约拉纳模式之间的间隔的数量级的距离时。在这里,我们研究了量子存储器的衰减时间编码在一个干净的拓扑纳米线与环境的相互作用,特别强调准粒子的传播以上的差距。我们表明,非本地编码不提供一个显着更长的相干时间比本地编码。特别地,传播的特征速度是纳米线的费米速度的量级,而不是由在间隙上方被激发的准粒子的慢得多的群速度给出。

英文摘要:

In order to increase the coherence time of topological quantum memories in systems with Majorana zero modes, it has recently been proposed to encode the logical qubit states in non-local Majorana operators which are immune to localized excitations involving the unpaired Majorana modes. In this encoding, a logical error only happens when the quasi-particles, subsequent to their excitation, travel a distance of the order of the spacing between the Majorana modes. Here, we study the decay time of a quantum memory encoded in a clean topological nanowire interacting with an environment with a particular emphasis on the propagation of the quasi-particles above the gap. We show that the non-local encoding does not provide a significantly longer coherence time than the local encoding. In particular, the characteristic speed of propagation is of the order of the Fermi velocity of the nanowire and not given by the much slower group velocity of quasi-particles which are excited just above the gap.

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