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arXiv 1407.5595cond-mat.supr-concond-mat.mes-hall
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低温下Josephson隧道结中的耗散

Dissipation in Josephson tunneling junctions at low temperatures

L. N. Bulaevskii, Shi-Zeng Lin

摘要:

了解基于约瑟夫森结的量子比特的退相干机制是非常重要的。在低温下,由于准粒子浓度呈指数级变小,人们需要考虑从隧穿电子到其他自由度的能量转移,以发现约瑟夫森结中的耗散和量子位中的退相干。本文讨论了两能级系统的能量转移,即在绝缘层中由势垒隔开的两种不同构型的离子之间的跃迁。我们导出了两个超导电极之间相位差的一般运动方程,并发现了一个由于电磁机制引起的延迟耗散项和电子隧穿机制的贡献。利用运动方程,我们计算了由于二能级系统的存在而引起的拉比振荡的衰减和量子比特的频移。在长时间范围内,我们的结果与Martinis等人[J. M. Martinis等人物理修订信函95,210503(2005)]在费米黄金法则范围内接近数值因子。

英文摘要:

It is important to know the decoherence mechanism of a qubit based on Josephson junctions. At low temperatures, as quasiparticle concentration becomes exponentially small, one needs to consider energy transfer from tunneling electrons to other degrees of freedom to find dissipation in Josephson junctions and decoherence in qubits. Here we discuss the energy transfer to two-level systems, i.e. the transitions between two different configurations of ions inside insulating layer separated by a potential barrier. We derive a general equation of motion for the phase difference between two superconducting electrodes and we find a retarded dissipation term due to electromagnetic mechanism and also contribution due to electron tunneling mechanism. Using the equation of motion we calculate the decay of Rabi oscillations and frequency shift in qubits due to the presence of the two-level systems. In the long time limit our results coincide with those obtained by Martinis et al. [J. M. Martinis et al.. Phys. Rev. Lett. 95, 210503 (2005)] within the Fermi's Golden rule approach up to a numerical factor.

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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