New regimes of quantum optomechanics using superfluid-filled cavities

该奖项支持的工作将寻求加深对如何使用光波来控制声波的理解，反之亦然。该团队将使用“光力学”控制来研究宏观物体的量子行为。这是基础科学和潜在技术应用特别感兴趣的领域。从一个基本的观点来看，量子力学定律描述了一个世界，在这个世界中，物体的行为可能就像它们同时在多个地方一样，在这个世界中，测量不可避免地会干扰被测量的物体。这些奇怪的效果在小物体的行为中最为明显，而且物体越大，效果就越模糊。然而，量子力学预测，这些效应可以在任何物体中观察到，只要它与热和摩擦足够隔绝，并且用足够的灵敏度进行测量。本课题将研究小体积超流体液氦运动中的量子效应。超流液氦可以冷却到极低的温度，并提供极低的摩擦水平。此外，超流体液氦与基于超灵敏激光的测量相兼容，非常适合诱导、控制和测量液体的量子运动。研究宏观物体（特别是液体物体）的量子运动将代表重要的科学进步，因为它将探索长期存在的问题，即我们在新一类物体中访问和控制量子效应的能力。它还将允许团队探索如何开发超流体光机械设备，用于先进的传感和通信技术等应用。该项目的目标是获得量子光力学的定性新体制。具体来说，该团队将研究宏观物体运动中的非高斯量子效应，无论是当这种运动可以用传统的正常模式来描述时，还是当这种描述被打破时。为了实现这一目标，他们将使用光机械装置，该装置由一个微型法布里-珀罗腔组成，该腔充满（或部分充满）超流体He。这项工作将以类似设备的先前成果为基础，并将结合新的概念和技术进步，以实现新的能力。这些进步可分为三类。首先，该团队将调整单光子和单声子探测技术，用于基于超流体的设备。其次，该团队将设计一种设备，在这种设备中，超流体体的表面波与高精细腔的光学模式耦合。第三，该团队将使用多模光力学耦合来研究具有强非互易性和非平凡拓扑特征的系统的量子行为。拟议的活动将在多个方面推进科学知识。访问和控制光力学系统中的非高斯态将使该小组能够执行迄今为止超出他们能力范围的广泛的量子传感和信息处理任务。提供对大质量物体中明显的量子效应的广泛访问，也将为测试与量子引力、离散时空和量子力学修正（如自发坍缩模型）相关的特定问题提供一条途径。测量多模器件中的高斯和非高斯量子效应，这些器件可以调谐到非互反和拓扑非平凡动力学，这也将是一个重要的进步。这是因为在经典状态下，耦合振子的常规正模描述在这样的系统中崩溃，绝热性的一些关键方面也是如此，目前尚不清楚这种崩溃将如何改变系统的量子行为。这凸显了探索这个系统所带来的发现机会。

The work supported by this award will seek to deepen the understanding of how light waves can be used to control sound waves, and vice versa. The team will use "optomechanical" control to study the quantum behavior of macroscopic objects. This is an area of particular interest for fundamental science and for potential technological applications. From a fundamental point of view, the laws of quantum mechanics describe a world in which objects may behave as though they are in multiple places at once, and in which measurements unavoidably disturb the object that is measured. These strange effects are most obvious in the behavior of small objects, and tend to become more obscured the larger the object is. Nevertheless, quantum mechanics predicts that these effects can be observed in any object that is sufficiently well isolated from heat and friction, and which is measured with sufficient sensitivity. In this project, quantum effects in the motion of a small volume of superfluid liquid helium will be studied. Superfluid liquid helium can be cooled to exceptionally low temperatures and offers extremely low levels of friction. Additionally, superfluid liquid helium is compatible with ultrasensitive laser-based measurements that are ideally suited to induce, control, and measure the liquid's quantum motion. Studying the quantum motion of macroscopic objects (and liquid objects in particular) will represent important scientific progress, as it will explore long-standing questions about our ability to access and control quantum effects in a new class of objects. It will also allow the team to explore the how to develop superfluid optomechanical devices for applications such as advanced sensing and communications technologies.The goal of the project is to access qualitatively new regimes of quantum optomechanics. Specifically, the team will study non-Gaussian quantum effects in the motion of macroscopic objects, both when this motion can be described in terms of conventional normal modes and when this description breaks down. To accomplish this, they will use optomechanical devices that consist of a miniature Fabry-Perot cavity filled (or partially filled) with superfluid liquid He. The work will build on prior results with similar devices and will combine new conceptual and technical advances in order to realize new capabilities. These advances fall into three categories. First, the team will adapt single-photon and single-phonon detection techniques for use with superfluid-based devices. Second, the team will engineer devices in which the surface waves of a superfluid body couple to the optical modes of a high-finesse cavity. Third, the team will use multimode optomechanical coupling to study the quantum behaviors of systems with strong non-reciprocity and non-trivial topological features. The proposed activity will advance scientific knowledge on multiple fronts. Accessing and controlling non-Gaussian states in optomechanical systems will enable the group to perform a broad class of quantum sensing and information processing tasks that to date have been out of their reach. Providing access to a wide range of distinctly quantum effects in massive objects will also provide a route towards testing specific questions related to quantum gravity, discrete space-time, and modifications of quantum mechanics (such as spontaneous collapse models). Measuring Gaussian and non-Gaussian quantum effects in multimode devices that can be tuned to access non-reciprocal and topologically non-trivial dynamics will also represent an important advance. This is because in the classical regime, the conventional normal mode description of coupled oscillators breaks down in such systems, as do some key aspects of adiabaticity, and it is unclear at present how this breakdown will alter the system's quantum behavior. This highlights the opportunities for discovery that will come from exploring this system.