Quantum Superposition States of a Mirror

镜子的量子叠加态

• 批准号: 0504825
• 负责人: Dirk Bouwmeester
• 金额: $ 36万
• 依托单位: University of California-Santa Barbara
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-08-01 至 2008-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0504825&HistoricalAwards=false
• 关键词: Quantum; Superposition; States; Mirror

Quantum Mechanics is based on a wave-mechanical description of a system and on the von Neumann postulate (1920s) that a quantum measurement results in an indeterministic outcome. The wave-mechanical description allows for superposition states of a system (e.g. an object being in two places at the same time), and the von Neumann postulate implies that one cannot directly detect such a superposition. Models of environmental induced decoherence do give an explanation of why quantum superpositions are not observed in everyday life, however the indeterministic nature of the measurement outcome is still the topic of many debates. The aim of this research proposal is to create a quantum superposition states involving of order 10^14 atoms. Such quantum superposition states will be ten orders of magnitude more massive than any quantum superposition observed to date and will therefore provide a fundamental test of quantum mechanics in a new regime.The experiment contains a tiny mirror (smaller in diameter than the thickness of a human hair) that is part of an optical cavity, which forms one arm of an interferometer. The mirror is mounted on a tiny Silicon rod and can be displaced by the multiple reflections of a photon. A single photon is sent into the interferometer and will evolve into a superposition of being inside the optical cavity with the tiny mirror, thereby slightly displacing it, and being in the other arm of the interferometer, leaving the mirror at rest. The superposition of a single photon is therefore transferred to a superposition of the mirror, or more precise, the mirror becomes entangled with the photon. By observing the interference of the photon leaving the interferometer one can study the creation and decoherence of superpositions involving the mirror. Preliminary experiments have been supported by a one-year NSF exploratory-research grant and led to remarkable initial progress; a high-quality Bragg mirror of diameter 20 microns has been fabricated using a focussed ion beam and has been positioned onto a Silicon cantilever [tip of an atomic force microscope (AFM)]. The cantilever/mirror system has been piezo-positioned to be the end mirror of an optical cavity. Measurements in air showed an initial cavity finesse of 1000.The individual components of the precision measurement system will be of interest for applications in many other fields with direct benefits to society. Anticipated spin-off projects are ultra-fast switchable mirrors (for optical communication), ultra-high resolution AFM readout, and optical cooling of micro-mechanical oscillators (for position measurements). The project will provide excellent training since it combines fundamental research interests with cutting-edge technologies. Since the project involves different subprojects, it is the intention to have several undergraduate researchers assisting the project each summer, as well a high-school students participating in the UCSB summer science education program.

量子力学基于系统的波动力学描述和冯·诺依曼假设（1920年代），即量子测量导致不确定性结果。波动力学的描述允许系统的叠加态（例如，一个物体同时在两个地方），而冯·诺依曼假设意味着人们不能直接检测到这样的叠加。环境诱导退相干模型确实解释了为什么量子叠加在日常生活中无法观察到，但是测量结果的不确定性仍然是许多争论的话题。这项研究计划的目的是创造一个包含10^14个原子的量子叠加态。这种量子叠加态的质量将比迄今为止观测到的任何量子叠加态都大10个数量级，因此将在一个新的领域提供量子力学的基本测试。该实验包含一个微小的镜子（直径比人类头发的厚度还小），它是光学腔的一部分，构成干涉仪的一个臂。镜子安装在一个微小的硅棒上，可以通过光子的多次反射来移动。一个光子被送入干涉仪，并将演变成一个叠加，在光学腔内与微小的反射镜，从而轻微地移动它，并在干涉仪的另一个臂，离开反射镜静止。因此，单个光子的叠加被转换为镜子的叠加，或者更准确地说，镜子与光子纠缠在一起。通过观察离开干涉仪的光子的干涉，人们可以研究涉及反射镜的叠加的产生和退相干。初步实验得到了为期一年的NSF探索研究资助的支持，并取得了显着的初步进展;使用聚焦离子束制造了直径为20微米的高质量布拉格镜，并将其放置在硅悬臂上[原子力显微镜（AFM）的尖端]。悬臂梁/反射镜系统已被压电定位为光学腔的端镜。在空气中的测量表明，初始腔精细度为1000。精密测量系统的各个组件将在许多其他领域的应用与直接社会效益的兴趣。预期的副产品项目是超快速可切换反射镜（用于光通信），超高分辨率AFM读数和微机械振荡器的光学冷却（用于位置测量）。该项目将提供出色的培训，因为它将基础研究兴趣与尖端技术相结合。由于该项目涉及不同的子项目，它是打算有几个本科研究人员协助该项目每年夏天，以及高中学生参加UCSB夏季科学教育计划。