Fundamental science and technology with levitated cavity optomechanics

技术进步允许使用光对机械振荡器的运动进行极其精细的测量和控制，这导致了最近的几项科学突破。值得注意的例子是LIGO天文台，这是一个公里级的光学机械系统，能够测量比原子核尺寸小1000倍的位移。LIGO是有史以来最灵敏的仪器之一，因首次探测到引力波而获得2017年诺贝尔奖，它继续取得非凡的成果，包括在2020年探测到量子涨落对10公斤质量运动的影响。尽管尺度要小得多，腔微光学机械系统可以被视为表-最好的类似物，因为它们采用了类似的物理原理，并采用了LIGO的几种技术策略，以减少测量的反作用和仪器噪音降到海森堡尺度附近。这些实验室规模的光机械系统本身也取得了重要进展，包括在过去几个月里，两个振荡膜之间的量子纠缠的演示，这是基础物理和应用中测量和传感的关键量子资源。值得注意的是，在光机械的活跃领域，悬浮在光场中的纳米粒子正在产生相当大的兴奋，最近有三个独立的演示，其质心运动的一个自由度从室温（300开尔文）冷却到比其最低可能能量（微K）高不到一个量子。真空中的悬浮形成了一个纳米振荡器，它是非常好的隔离，使其成为超弱力的量子限制测量的理想选择。它们为从商业传感器到量子技术再到基础物理研究（包括寻找奇异物质态）的应用提供了可能性。我们提议开创悬浮腔光学力学的多粒子和多体机制，将该领域推向一个新的方向，并利用多个相同且完全可控的纳米振荡器的独特可扩展性。在基础科学或量子技术之外，核心目标是控制非球形纳米粒子的取向，以实现衍射成像。因此，该项目开辟了从多体量子动力学在一个新的制度，以实际应用中的纳米粒子表征的方式。我们将实现这一目标，通过建立我们在这一领域的专业知识，包括为这个建议，证明新的相干散射为基础的战略的可行性进行的原理验证实验。具体来说，我们将使用紧密耦合的实验和理论方法，旨在实现对单个粒子所有运动自由度的完全量子控制。这不仅包括单个粒子的3D平移运动，还包括旋转和平移运动。我们将开发协议，用于生成和测量2个或更多个粒子的运动之间的相关性，并实施和研究相同的悬浮粒子在一个腔体内的1D和2D阵列。

Technical advances allowing extremely fine measurement and control of the motion of mechanical oscillators, using light, have led to several recent scientific breakthroughs. Notable examples are due to the LIGO observatory, a kilometre scale optomechanical system capable of measuring dis-placements 1000 times smaller than the dimension of a nucleus. Awarded the 2017 Nobel prize for the first detection of gravitational waves, LIGO -one of the most sensitive instruments ever built- continues to deliver extraordinary results, including the detection in 2020 of the effects of quantum fluctuations on the motion of a ten kilogram mass.Though on much smaller scales, cavity micro-optomechanical systems might be viewed as table-top analogues since they employ similar physical principles and have adapted several of the technical strategies of LIGO to reduce measurement back action and instrumental noises down to near the Heisenberg scale. These laboratory-scale optomechanical systems are themselves yield-ing important advances including, in the last few months, the demonstration of quantum entanglement between two oscillating membranes, a key quantum resource for measurement and sensing in both fundamental physics and applications.Remarkably, within the active field of optomechanics, nano-particles levitated in a optical field are generating considerable excitement, with three independent recent demonstrations of cooling of one degree of freedom of its centre-of-mass motion from room temperature (300 Kelvin) to within less than a quantum above its lowest possible energy (microK). Levitation in vacuum forms a nano-oscillator that is extremely well isolated making it ideal for quantum-limited measurement of ultra weak forces. They offer possibilities for applications that range from commercial sensors to quantum technologies to studies of fundamental physics, including the search for exotic states of matter.We are proposing to pioneer many-particle and many-body regimes of levitated cavity optomechanics, taking the field in a new direction and capitalising on the unique scalability of to multiple identical and fully controllable nano-oscillators. Beyond basic science or quantum technology, a core objective is to develop control of the orientation of nonspherical nanoparticles for diffraction imaging. Thus the project opens the way to ranging from many-body quantum dynamics in a novel regimes to practical applications in nanoparticle characterisation.We will achieve this goal by building on our expertise in this area including proof-of-principle experiments performed for this proposal that demonstrate the viability of the new coherent scattering-based strategies. Specifically, we will use a tightly coupled experimental and theoretical approach, that aims to realise full quantum control over all motional degrees of freedom of the single particle as our point of departure. This includes not only 3D translational but also rotational and librational motion of a single particle. We will develop protocols for generation and measurement of correlations between the motion of 2 or more particles and implement and investigate 1D and 2D arrays of identical levitated particles within a cavity.