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Quantum feedback control of levitating opto-mechanics

悬浮光力学的量子反馈控制

基本信息

批准号：
EP/K026267/1
负责人：
Alessio Serafini
金额：
$ 73.9万
依托单位：
University College London
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2013
资助国家：
英国
起止时间：
2013 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=EP%2FK026267%2F1
关键词：
Quantum feedback control levitating opto

项目摘要

When confronted with the task of controlling a physical degree of freedom, observations and adjustments based on such observations are a most natural way to proceed. This is the basic idea behind the notion of feedback control, one of the standard paradigms of control engineering. If applied to systems subject to continuous noise, feedback control loops driven by continuous monitoring often allow one to cancel the effect of noise and to stabilise the system in a desirable configuration, up to a certain precision. Such powerful control routines are well established for macroscopic objects, obeying the laws of classical mechanics. However, it is becoming more and more desirable to extend the application of feedback control to microscopic degrees of freedom, governed by quantum mechanics. Due to the fundamentally probabilistic character of quantum mechanics, the observation of quantum objects typically results in a distribution of probabilistic outcomes, which manifests itself as additional noise (technically referred to as measurement back-action). This feature makes the theory of quantum feedback control, whereby quantum degrees of freedom are monitored and steered to desired states, rather more complex than its classical counterpart. Yet, the design and implementation of quantum feedback control schemes would be most timely and welcome, given the current struggle to achieve coherent manipulations for application in nano- and quantum technologies. The main obstacle standing in the way of exploitable quantum computation is still the problem of engineering multipartite microscopic systems where the interactions between the controlled subsystems are enhanced, while the unwanted interaction with their environment is suppressed. Feedback control schemes would offer an active way to suppress the effect of such environmental noise, with the possibility of stabilising the systems in quantum states useful as resources for quantum information processing.Recent advances in cooling, trapping and manifacturing techniques are bringing more and moredegrees of freedom into the quantum regime. Among such degrees of freedom the family of cavity opto-mechanical systems, where resonating light is coupled to a micro- or nano-scopic mechanical oscillator, stand out for their interest in sensing, quantum information processing and as probes of the quantum to classical boundary (as they include massive oscillators of varying size). In particular, a new generation of such systems recently emerged where the mechanical oscillator is not clamped to a substrate but is instead a levitating bead, trapped by optical means. These set-ups are particularly promising because they are not influenced by the thermal fluctuations of a substratum. Still, because of their relatively low frequencies, which set much more stringent cooling requirements, they have not yet entered a fully quantum regime, where coherent, pure quantum states can be manipulated and observed. They would hence benefit greatly from the development of bespoke feedback control techniques.Our research project is aimed at the design and implementation of feedback schemes for the cooling and quantum control of opto-mechanical systems, and in particular for the levitated bead set-ups at University College London and at the University of Vienna (project partner). We intend to achieve ground state cooling as well as squeezed states (states where the uncertainty on position is below the uncertainty of the ground state, of relevance to quantum metrology), as well as non-classical superpositions (Schroedinger cats) of the levitated beads.

当面临控制物理自由度的任务时，基于这种观察和调整是最自然的方法。这是反馈控制概念背后的基本思想，是控制工程的标准范例之一。如果应用于受连续噪声影响的系统，由连续监测驱动的反馈控制回路通常允许人们消除噪声的影响，并将系统稳定在理想的配置中，达到一定的精度。这种强大的控制程序是为宏观物体建立的，遵循经典力学定律。然而，将反馈控制的应用扩展到由量子力学控制的微观自由度是越来越可取的。由于量子力学的基本概率特征，对量子物体的观察通常会导致概率结果的分布，这表现为额外的噪声（技术上称为测量反作用）。这一特性使得量子反馈控制理论——量子自由度被监控并引导到理想状态——比其经典对应理论更为复杂。然而，量子反馈控制方案的设计和实现将是最及时和受欢迎的，考虑到目前在纳米和量子技术应用中实现相干操作的斗争。阻碍可利用量子计算的主要障碍仍然是工程多部微观系统的问题，其中被控制子系统之间的相互作用得到增强，而与环境的不必要的相互作用被抑制。反馈控制方案将提供一种主动的方式来抑制这种环境噪声的影响，并有可能将系统稳定在量子态，作为量子信息处理的有用资源。冷却、俘获和制造技术的最新进展正在给量子体系带来越来越多的自由度。在这些自由度中，谐振光耦合到微或纳米级机械振荡器的腔光机械系统家族因其在传感，量子信息处理和量子到经典边界的探针方面的兴趣而脱颖而出（因为它们包括不同尺寸的巨大振荡器）。特别是，最近出现了新一代这样的系统，其中机械振荡器不是夹在基板上，而是一个悬浮的头，通过光学手段被捕获。这些装置特别有前途，因为它们不受基底热波动的影响。然而，由于它们的频率相对较低，对冷却的要求要严格得多，它们还没有进入完全的量子状态，在这个状态下，相干的、纯的量子态可以被操纵和观察。因此，他们将从定制反馈控制技术的发展中受益匪浅。我们的研究项目旨在设计和实施反馈方案，用于光机械系统的冷却和量子控制，特别是在伦敦大学学院和维也纳大学（项目合作伙伴）的悬浮头装置。我们打算实现基态冷却和压缩态（与量子计量相关的位置不确定性低于基态不确定性的状态），以及悬浮珠的非经典叠加（薛定谔猫）。