NIRT: Nanoscale Quantum Systems: Excitations and Control

该提案是响应纳米科学与工程倡议，NSF-01-157，纳米跨学科研究小组（NIRT）。 该奖项由美国国家科学基金会材料研究、数学科学和物理部门共同资助。纳米级电子器件的设计、开发和控制提出了许多具有挑战性的问题，特别是在远离平衡的量子系统领域。 这样的介观器件通常与它们的环境弱耦合，因此平衡是困难的。 共同的问题是由不同的问题，包括量子点，驱动约瑟夫森结和有限尺寸的量子玻璃共享。 现在存在远离平衡的可控量子系统，理论和实验都可以达到。 在这项研究中，来自罗格斯大学，普林斯顿大学和NEC的理论家团队将通过一系列具体研究来解决这一领域的全球问题，利用非平衡自旋系统和无序相互作用电子之间的概念联系。强调了为了优化纳米电路的性能，必须更好地理解电子退相干的非平衡源，特别是涉及量子动力学的纳米电路，非平衡量子动力学问题可以用局域化理论来解决。 量子玻璃的动力学可以用粒子在高维球上的随机势中的运动来描述。 这样的系统显示扩散行为，从本地化的角度来看是不期望的。 这种矛盾将被调和。在低密度无序绝缘体中的电荷输运显示出缓慢的弛豫，表明系统无法找到基态。 它的复自由能是由于库仑相互作用和随机势之间的竞争。 该团队将采用类似于自旋玻璃的方法，识别并求解一个描述孤立电子系统中局域化-离域化跃迁的模型。为了控制相位相干性，必须更好地理解电子退相的来源。 这个问题对于量子电路的构建至关重要;即使每个元件都被优化设计，也存在集体退相的可能性。 一个相关的问题是识别一个单一的量子位，其中退相干最小化。 具有双简并基态和带隙的自旋液体可能是一个有吸引力的候选者，因为它缺乏长程有序性，有效地将其从外部环境中分离出来。 该提案是响应纳米科学与工程倡议，NSF-01-157，纳米跨学科研究小组（NIRT）。 该奖项由美国国家科学基金会材料研究、数学科学和物理部门联合资助，这支由罗格斯大学、普林斯顿大学和NEC的理论家组成的互补团队将联合收割机他们的才能结合起来，研究与纳米尺度量子电子动力学有关的基本问题。 随着电路接近纳米尺度，这些问题变得更加关键，特别是当它们涉及到纳米器件中的相位相干性问题及其在量子计算机中的可能应用时。

This proposal was received in response to the Nanoscale Science and Engineering Initiative, NSF-01-157, Nanoscale Interdisciplinary Research Teams (NIRT). The award is funded jointly by the NSF Divisions of Materials Research, Mathematical Sciences and Physics.The design, development and control of nanoscale electronics raises many challenging questions, particularly in the area of quantum systems far from equilibrium. Such mesoscopic devices are often weakly coupled to their environment, so that equilibration is difficult. Common issues are shared by diverse problems including quantum dots, driven Josephson junctions and finite-size quantum glasses. There now exist controllable quantum systems far from equilibrium that are accessible to both theory and experiment. In this research, a team of theorists from Rutgers, Princeton and NEC will address global issues in this area through a series of specific studies, using the conceptual links between nonequilibrium spin systems and disordered interacting electrons. It is emphasized that nonequilibrium sources of electron decoherence must be better understood in order to optimize performance of nanoscale circuitry, especially that which involves quantum dynamics.The problem of nonequilibrium quantum dynamics can be approached using localization theory. The dynamics of a quantum glass can be described by particle motion in a random potential on a high-dimensional sphere. Such systems display diffusive behavior not expected from a localization perspective. This discrepancy will be reconciled.Charge transport in a low-density disordered insulator displays slow relaxation, indicative of the system's inability to find its ground-state. Its complex free energy is due to competition between Coulomb interactions and a random potential. Taking an approach analogous to that in spin glasses, the team will identify and solve a model describing the localization-delocalization transition in an isolated electronic system.Sources of electron dephasing must be better understood in order to control phase coherence. This issue is crucial for the construction of quantum circuitry; even if each element is designed optimally, there is the possibility of collective dephasing. A related problem is the identification of a single qubit where decoherence is minimized. A spin liquid with a doubly degenerate ground-state and a gap may be an attractive candidate, since its absence of long-range order effectively decouples it from the external environment.%%% This proposal was received in response to the Nanoscale Science and Engineering Initiative, NSF-01-157, Nanoscale Interdisciplinary Research Teams (NIRT). The award is funded jointly by the NSF Divisions of Materials Research, Mathematical Sciences and Physics.This complementary team of theorists from Rutgers, Princeton and NEC will combine their talents to study fundamental issues relating to quantum electron dynamics at the nanoscale. As electrical circuitry approaches the nanoscale these issues become more critical, particularly as they relate to problems of phase coherence in nanodevices and its possible application in quantum computers.***