论文标题
用超导量子量子探测环境自旋极化
Probing Environmental Spin Polarization with Superconducting Flux Qubits
论文作者
论文摘要
我们介绍了耦合到RF式通量量子量的磁通度的偏振磁环境的动力学测量值。量子位既用作偏振场的来源，又用作环境极化的探测器。我们从5 $ $ s到5 ms，在12.5至22 mk之间的时间尺度上探测动力学。测得的极化与温度与温度为$ 5.7 \ pm 0.3 $ mk的相位过渡提供了有力的证据。此外，环境极化最初以$ \ sqrt {t} $的形式增长，与自旋扩散动力学一致。但是，自旋扩散模型与长时间标准的数据偏离，这表明一种不同的现象是导致低频行为的原因。简单的$ 1/f $型号可以在所有时间尺度上适合数据，但需要经验的低频和高频截止。我们认为，这些结果与由随机旋转的环境一致，在簇中具有快速自旋扩散动力学，并且簇的总矩慢速波动。
We present measurements of the dynamics of a polarized magnetic environment coupled to the flux degree of freedom of rf-SQUID flux qubits. The qubits are used as both sources of polarizing field and detectors of the environmental polarization. We probe dynamics at timescales from 5 $μ$s to 5 ms and at temperatures between 12.5 and 22 mK. The measured polarization versus temperature provides strong evidence for a phase transition at a temperature of $5.7\pm 0.3$ mK. Furthermore, the environmental polarization grows initially as $\sqrt{t}$, consistent with spin diffusion dynamics. However, spin diffusion model deviates from data at long timescales, suggesting that a different phenomenon is responsible for the low-frequency behavior. A simple $1/f$ model can fit the data at all time scales but it requires empirical low- and high-frequency cutoffs. We argue that these results are consistent with an environment comprised of random clusters of spins, with fast spin diffusion dynamics within the clusters and slow fluctuations of the total moments of the clusters.
