受限量子导体中电子高频量子输运退相干机制的实验研究

Quantum coherent electronics for high frequency quantum transport in low dimensional confined systems is of fundamental interest in quantum information processing. The probe of the quantum dynamics of electrons has been a major challenge, for which fast manipulation and readout of charge states are needed. After years of painstaking research, we have successfully built the measurement system, which is appropriate for studying the high frequency electronic quantum transport in strong magnetic field, and experimentally studied dynamic transport in low dimensional confined conductors. Our experiments demonstrate that the quantized charge relaxation resistance is universal, i.e., Rq= h/2e^2, which requires global phase coherence. However, for a realistic system, the interaction of the electrons with its physical environment is unavoidable, which triggers a transition of dynamical transport form a quantum coherent to a classical regime, thus provoking a deviation from the universal Rq. In this project, mesoscopic capacitors with different structures will be fabricated. We will experimentally investigate on the quantum dynamics of the quantum capacitors based on factors related to the electronic coherent transport such as material properties, temperature and electron interactions. The gigahertz frequency dynamic admittance of quantum dots will be measured to obtain important physical quantities for electron temperature and interaction parameters. We will focus on the effects of electron-electron interactions on the charge relaxation resistance and further explore its quantum to classical transition. Through the implementation of this research, it is expected to clarify the mechanism of electronic decoherence of dynamic quantum transport in confined quantum system, and the results will be of guidance significance for designing and manipulating ultrafast operations in quantum devices.

低维受限体系中量子相干效应主导的高频量子输运，是未来量子信息技术的物理基础。它要求超快地操控和测量电子的量子输运行为，这和稳态量子输运比较起来是一个极大的挑战。为此，我们建成了极低温强磁场高频测量系统，研究了量子导体的高频量子输运特性，观察到了源自电子相干运动的普适量子化电荷弛豫电阻h/2e^2。然而，在实际的体系中电子不可避免地与外界环境相互作用，从而失去量子相干性，破坏弛豫电阻的普适性。本项目拟从影响电子相干输运过程的材料特性、温度、电子相互作用等要素出发，研制不同结构的介观量子电容，对其量子动力学特性进行较系统的研究。通过测量量子点的动态复数导纳确定电子温度和相互作用参数等重要物理量，重点研究弛豫电阻受电子-电子相互作用影响的规律，探索量子化电荷弛豫电阻向经典电阻转变的机理。本项目研究有望阐明受限量子体系中高频量子输运的退相干机制，研究结果将有助于量子器件超快操控的设计和实现。

随着IT芯片技术的发展，集成度提高，半导体器件不断小型化并趋于纳米尺度。电子运动是弹道式的运动，其电子波函数的相位具有相干性,从而这种量子器件的电磁特性具有明显的量子行为。例如，基于新型量子器件的电路，由于电子在量子点、谐振腔中的相互作用，电子的居留时间和高频电磁场的周期的关联，以及电子弹性碰撞的弛豫过程，产生了崭新的量子电阻和量子电感。这些新的量子参量和原有的经典参量叠加，势必出现新的物理效应。低维受限体系中量子相干效应主导的高频量子输运，是未来量子信息技术的物理基础。它要求超快地操控和测量电子的量子输运行为。.然而，在实际的体系中电子不可避免地与外界环境相互作用，从而失去量子相干性，破坏弛豫电阻的普适性。本项目从影响电子相干输运过程的材料特性、温度、电子相互作用等要素出发，研制不同结构的介观量子电容，对其量子动力学特性进行较系统的研究。通过测量量子点的动态复数导纳确定电子温度和相互作用参数等重要物理量，重点研究弛豫电阻受电子-电子相互作用影响的规律，探索量子化电荷弛豫电阻向经典电阻转变的机理。.本项目中我们搭建了高频量子阻抗测量系统，其能够测量够测量数千兆赫兹频率范围内功率大于-130 dBm的高频微弱量子信号。利用国产材料成功研制了基于半导体异质结的量子阻抗器件，观察到了源自电子相干运动的普适量子化电荷弛豫电阻h/2e^2。实验证实了量子点内存在强电子-电子相互用条件下，电荷弛豫电阻在相干区仍不随栅电压改变。实验观察到介观电容器处于完全开通量子通道的量子电容振荡行为，且振荡幅度随温度和磁场的增加而迅速的减少。实验表明这种电容振荡是介观相干效应，它是由于在几乎开通的量子点中的电子干涉而产生的。.本项目研究较系统地阐明受限量子体系中高频量子输运的退相干机制，研究结果有助于量子器件超快操控的设计和实现。