论文标题
在组合踢的转子和量子步行系统中的量子传输
Quantum transport in a combined kicked rotor and quantum walk system
论文作者
论文摘要
我们对两种相反的干扰效应(即一方面干扰诱导的弹道传输)与另一方面强(Anderson)定位之间的竞争进行了理论和数值研究。虽然前者允许无电阻运输,但后者将运输带到了完整的停顿。作为模型系统,我们考虑了量子踢转子,其中在离散动量坐标中观察到强烈的定位。在此模型中,我们以hadamard量子步行的形式引入了弹道传输。两种传输机制是通过交替交替的Floquet运算符组合的。扩展了踢旋翼的相应计算,我们估计了结合动力学的经典扩散系数。然后,基于引入有效的海森堡时间的另一个论点,应允许估算本地化时间和定位长度。虽然众所周知,在踢旋翼的情况下,这在我们的案例中会失败。尽管组合的动态仍显示出本地化,但它发生在更大的时间,并且显示出比预测的更大的定位长度。最后,我们将踢动的转子与其他类型的量子步道相结合,即扩散和本地化的量子步行。在扩散的情况下,踢旋翼的本地化动力学被完全取消,我们得到了纯粹的扩散。在本地化量子步行的情况下,组合系统保持本地化,但定位长度较大。
We present a theoretical and numerical study of the competition between two opposite interference effects, namely interference-induced ballistic transport on one hand, and strong (Anderson) localization on the other. While the former effect allows for resistance free transport, the latter brings the transport to a complete halt. As a model system, we consider the quantum kicked rotor, where strong localization is observed in the discrete momentum coordinate. In this model, we introduce the ballistic transport in the form of a Hadamard quantum walk in that momentum coordinate. The two transport mechanisms are combined by alternating the corresponding Floquet operators. Extending the corresponding calculation for the kicked rotor, we estimate the classical diffusion coefficient for thecombined dynamics. Another argument, based on the introduction of an effective Heisenberg time should then allow to estimate the localization time and the localization length. While this is known to work reasonably well in the kicked rotor case, we find that it fails in our case. While the combined dynamics still shows localization, it takes place at much larger times and shows much larger localization lengths than predicted. Finally, we combine the kicked rotor with other types of quantum walks, namely diffusive and localizing quantum walks. In the diffusive case, the localizing dynamics of the kicked rotor is completely canceled and we get pure diffusion. In the case of the localizing quantum walk, the combined system remains localized, but with a larger localization length.