Decoherence of a quantum two-level system by spectral diffusion
Decoherence of a quantum two-level system by spectral diffusion
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DOI：
10.1103/physrevb.93.134208
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发表时间：
2016-02
影响因子：
3.7
通讯作者：
S. Matityahu;A. Shnirman;G. Schon;M. Schechter
中科院分区：
文献类型：
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作者：
S. Matityahu;A. Shnirman;G. Schon;M. Schechter
我们研究了一个单独的高频隧穿二能级系统（TLS）的退相，由于其与标准隧穿模型（STM）描述的低频热TLS的合奏相互作用。我们表明，由浴的TLS的退相解释了对外部施加的应变以及其数量级的拉姆齐退相速率的依赖性，在最近的实验中观察到[J. Lisenfeld等人]。然而，基于STM的理论预测哈恩回波协议要有效得多，与实验相比，产生太低的回波移相率。此外，STM预测的回波移相速率的应变依赖性与测量的二次依赖性不一致，这将适合于高频白色噪声环境。我们认为，很少有比STM的通常的TLS更强地耦合到应变场的快速TLS引起这样的白色噪声。这解释了实验中观察到的回波移相速率的幅度和强烈波动。
We study the dephasing of an individual high-frequency tunneling two-level system (TLS) due to its interaction with an ensemble of low-frequency thermal TLSs which are described by the standard tunneling model (STM). We show that the dephasing by the bath of TLSs explains both the dependence of the Ramsey dephasing rate on an externally applied strain as well as its order of magnitude, as observed in a recent experiment [J. Lisenfeld et al.]. However, the theory based on the STM predicts the Hahn-echo protocol to be much more efficient, yielding too low echo dephasing rates, as compared to the experiment. Also the strain dependence of the echo dephasing rate predicted by the STM does not agree with the measured quadratic dependence, which would fit to a high-frequency white noise environment. We suggest that few fast TLSs which are coupled much more strongly to the strain fields than the usual TLSs of the STM give rise to such a white noise. This explains the magnitude and strong fluctuations of the echo dephasing rate observed in the experiment.