Decoherence & Correlations in Condensed Matter Systems

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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).**********