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Decoherence of an electronic and macroscopic superposition state by interaction with a superconductor

与超导体相互作用导致电子和宏观叠加态的退相干

基本信息

批准号：
265596161
负责人：
Dr. Alexander Stibor
金额：
--
依托单位：
Physikalisches Institut
依托单位国家：
德国
项目类别：
Research Grants
财政年份：
2015
资助国家：
德国
起止时间：
2014-12-31 至 2020-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/265596161?language=en
关键词：
Decoherence electronic macroscopic superposition state

项目摘要

The analysis of the transition from a quantum mechanical to a classical system is part of the foundations of modern physics. This loss of quantum properties is described by the theory of decoherence. It is of fundamental and technical relevance, e.g. for the implementation of hybride quantum systems. In this project a model system will be realized, where a macroscopic and electronic superposition state in a biprism interferometer couples to a superconducting environment by Coulomb interaction. Thereby an electron wave gets separated and combined coherently by a thin electrostatically charged wire. Before the partial waves overlap and interfere, they traverse a superconducting surface in a variable distance of a few ten micrometers. This results in a Coulomb interaction between the electronic matter wave and the Cooper pairs in the superconductor. It has a direct influence to decoherence of the superposition state that can be measured by a contrast loss in the interference pattern. In the planned project the electric resistance disappears completely in the surface because of the applied superconductor, in contrary to former decoherence experiments with electrons nearby semiconducting surfaces. It was shown for semiconductors that due to the formation of image charges below the electron paths, exactly this resistance leads to a which-path-information to the environment and consequently to decoherence. Various theoretical models assume a dissipative term for the friction of the image charge, as a consequence of the electric resistance in the material. A gradual loss of contrast is therefore observed with increasing distance between the electron pathways and with decreasing distance to the surface. However, the properties of the electronic superposition state above the superconductor cannot be described with previous theories. It will be studied experimentally in detail within this project.Furthermore open questions will be concerned according decoherence of such an electronic superposition state above metallic and variable doped semiconducting surfaces. Previous predictions could only provide a description of the measured decoherence distribution above a certain semiconductor but not for the strength of decoherence. It will be measured in the current approach above surfaces with electric resistivities that can be varied by up to nine orders of magnitude. It is theoretically assumed, that decoherence depends also on the temperature of the surface. Therefore decoherence of the superposed electronic state will be measured with surface temperatures between 4 and 500 K. The results will then be compared to current decoherence models. The aim is to develop thereby a correct description of the decoherence mechanisms near conducting and superconducting surfaces.

从量子力学到经典系统的过渡分析是现代物理学基础的一部分。这种量子特性的损失可以用退相干理论来描述。它具有基础和技术相关性，例如用于混合量子系统的实现。在这个计画中，我们将实现一个模型系统，其中在双棱镜干涉仪中的宏观与电子叠加态通过库仑作用耦合到超导环境中。因此，一个电子波得到分离，并通过一个细的静电充电线相干组合。在分波重叠和干涉之前，它们以几十微米的可变距离穿过超导表面。这导致电子物质波和超导体中的库珀对之间的库仑相互作用。它对叠加态的退相干有直接影响，可以通过干涉图样中的对比度损失来测量。在计划中的项目中，由于应用了超导体，表面的电阻完全消失，这与以前在半导体表面附近进行的电子退相干实验相反。对于半导体来说，由于在电子路径下方形成了图像电荷，正是这种电阻导致了环境中的哪条路径信息，从而导致了退相干。各种理论模型假设图像电荷的摩擦的耗散项，作为材料中的电阻的结果。因此，随着电子路径之间的距离的增加和到表面的距离的减小，观察到对比度的逐渐损失。然而，超导体上方的电子叠加态的性质不能用以前的理论来描述。本项目将在实验上进行详细的研究，并根据金属和可变掺杂半导体表面上的这种电子叠加态的退相干性，进一步关注尚未解决的问题。以前的预测只能提供测量到的退相干分布在某一半导体上的描述，但不能提供退相干强度的描述。它将在表面以上的电流方法中测量，其电介电常数可以变化多达九个数量级。理论上假定，退相干还取决于表面的温度。因此，叠加电子态的退相干将在4 - 500 K的表面温度下测量。然后将结果与当前的退相干模型进行比较。其目的是发展，从而正确的描述附近的导电和超导表面的退相干机制。