Decoherence & Correlations in Condensed Matter Systems

量子系统显示出“纠缠”(即两个不同的物理系统即使相距遥远，似乎也会协同行动--爱因斯坦称之为“远距离的诡异作用”)和**位相相干的过程。“退相干”描述了纠缠和相位相干被破坏的机制。如果我们要制造量子计算机(在量子计算机中它需要被抑制)，就需要理解退相干。退相干机制在物理学家构建的人工系统和自然界(特别是光合作用和动物和鸟类导航)中都发挥着至关重要的作用。本项目将集中于：**(1)退相干的应用工作：超导体和半导体、无序固体和自旋系统中的退相干机制，重点是(A)量子比特系统(磁性分子、量子点、超导体)的潜在**候选者和(B)量子力学基础测试的候选者(光学机械系统、量子孤子)，以及(C)生物系统(光合作用捕光分子、化学罗盘分子)的**退相干。它还将涉及生物系统中极化子和激子的微观理论，**以及偶极自旋系统和无序介质的动力学。**(2)退相干的一般模型：‘自旋浴’和‘振子浴’模型，‘第三方退相干’，量子临界系统中的退相干，以及磁和超导量子**孤子；**本项目的目标是一种完全可预测的固态和生物系统中的消相干理论，应用于这些领域的关键问题(量子比特系统中的消相干，宏观量子相干；磁性、超导、半导体系统中的消相干，以及光合作用和导航中的消相干)。

Quantum systems show 'entanglement' (a process whereby two distinct physical systems, even when widely separated, appear to act in concert - what Einstein called 'spooky action at a distance') and**also phase coherence. 'Decoherence' describes the mechanisms by which entanglement and phase coherence are destroyed. An understanding of decoherence is required if we are to ever make quantum computers (where it needs to be suppressed). Decoherence mechanisms play a crucial role in both the artificial systems constructed by physicists, and in the Natural world (notably in photosynthesis and in animal and bird navigation). This project will focus on:** (1) Applied work on decoherence: mechanisms of decoherence in superconductors and semiconductors, in disordered solids, and in spin systems, with emphasis on (a) potential**candidates for qubit systems (magnetic molecules, quantum dots, superconductors) and (b) candidates for fundamental tests of quantum mechanics (optomechanical systems, quantum solitons), and (c)**decoherence in biological systems(photosynthetic light-harvesting molecules, 'chemical compass' molecules). This will also involve microscopic theory for polarons and excitons in biological systems,**and the dynamics of dipolar spin systems and disordered dielectrics.** (2) General Models of Decoherence: the 'spin bath' and oscillator bath' models, '3rd-party decoherence', decoherence in quantum critical systems, and for magnetic and superconducting quantum**solitons; and theory enabling the separation of environmental decoherence from 'intrinsic decoherence' processes such as gravitational decoherence.** The goal of this project is a fully predictive theory of decoherence in solid-state & biological systems, to be applied to key problems in these fields (decoherence in qubit systems, macroscopic quantum coherence; decoherence in magnetic, superconducting, semiconducting systems, & in photosynthesis and navigation).**********