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利用光波控制声波以及如何利用光波控制声波的理解。该团队将使用“光学机械”控制来研究宏观物体的量子行为。对于基础科学和潜在的技术应用来说，这是一个特别感兴趣的领域。从根本上讲，量子力学定律描述了这样一个世界，在这个世界里，物体可能会表现得就像它们同时在多个地方一样，而且测量结果不可避免地会干扰被测量的物体。这些奇怪的效果在小对象的行为中最为明显，对象越大，这些效果往往会变得越模糊。然而，量子力学预测，这些效应可以在任何与热和摩擦隔绝得足够好、测量足够灵敏的物体上观察到。在这个项目中，我们将研究小体积超流液氦运动中的量子效应。超流液氦可以冷却到极低的温度，并提供极低的摩擦力。此外，超流液氦与基于激光的超灵敏测量兼容，非常适合于诱导、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)的量子运动将代表着重要的科学进步，因为它将探索关于我们在一类新物体中获取和控制量子效应的长期存在的问题。它还将使该团队能够探索如何为先进的传感和通信技术等应用开发超流体光学机械设备。该项目的目标是获得质量上的量子光学机械的新制度。具体地说，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描述时，还是当这种描述被打破时。为了做到这一点，他们将使用光学机械设备，其中包括一个充满(或部分填充)超流体液体He的微型法布里-珀罗腔。这项工作将建立在类似设备先前成果的基础上，并将结合新的概念和技术进步，以实现新的能力。这些进展可分为三类。首先，该团队将调整单光子和单声子探测技术，以用于基于超流体的设备。其次，该团队将设计一种装置，在这种装置中，超流体物体的表面波与高精细腔的光学模式相耦合。第三，该团队将使用多模光机械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促进科学知识。在光学机械系统中访问和控制非高斯态将使该小组能够执行迄今为止他们无法完成的广泛类别的量子传感和信息处理任务。提供对大质量物体中广泛的明显量子效应的访问，也将提供一条测试与量子重力、离散时空和量子力学修改(如自发坍塌模型)相关的特定问题的途径。测量多模器件中的高斯和非高斯量子效应也将代表着一项重要的进步。多模器件可以调谐到非互易和拓扑上的非平凡动力学。这是因为在经典系统中，耦合振子的常规简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，目前还不清楚这种崩溃将如何改变系统的量子行为。这凸显了探索这一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.