Decoherence and radiation-free relaxation in Meissner transmon qubit coupled to Abrikosov vortices
Decoherence and radiation-free relaxation in Meissner transmon qubit coupled to Abrikosov vortices
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DOI：
10.1103/physrevb.94.165128
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发表时间：
2016-10-14
影响因子：
3.7
通讯作者：
Bezryadin, Alexey
中科院分区：
文献类型：
--
作者：
Ku, Jaseung;Yoscovits, Zack;Bezryadin, Alexey
我们提出了一种可以通过相邻超导薄膜电极中的迈斯纳屏蔽电流来调谐的跨导分裂结量子比特。最好的检测弛豫时间（T-1）是50 μ s的数量级和失相时间（T-2）约40 μ s。与通常的基于SQUID的transmon量子比特相比，所实现的磁场振荡周期要小得多，因此实现了强有效场放大。这个迈斯纳量子比特允许在量子比特结中流动的电流和由Abrikosov涡旋产生的电流的强烈混合。本文对耦合到Abrikosov涡旋的量子比特的无辐射弛豫进行了定量分析。相干量子振荡的观测提供了强有力的证据，证明涡旋的位置和速度不必接受精确的值，但可以在量子力学意义上被模糊。这种状态的最终弛豫有助于耦合到涡旋的量子位的弛豫速率增加。这种松弛描述使用的Caldeira-Leggett量子耗散理论的基本概念。
We present a type of transmon split-junction qubit which can be tuned by Meissner screening currents flowing in the adjacent superconducting film electrodes. The best detected relaxation time (T-1) was of the order of 50 mu s and the dephasing time (T-2) about 40 mu s. The achieved period of oscillation with magnetic field was much smaller than in the usual SQUID-based transmon qubits; thus a strong effective field amplification has been realized. This Meissner qubit allows a strong mixing of the current flowing in the qubit junctions and the currents generated by the Abrikosov vortices. We present a quantitative analysis of the radiation-free relaxation in qubits coupled to the Abrikosov vortices. The observation of coherent quantum oscillations provides strong evidence that the position of the vortex as well as its velocity do not have to accept exact values but can be smeared in the quantum mechanical sense. The eventual relaxation of such states contributes to an increased relaxation rate of the qubit coupled to vortices. Such relaxation is described using basic notions of the Caldeira-Leggett quantum dissipation theory.