Superfluid Optomechanics

在过去的几年里，光学力学领域取得了迅速的进步，从光学和机械系统之间的耦合的原理证明演示，到在少数这样的设备上观察量子效应。在同一时期，光学机械系统与其他AMO系统(如超冷原子和钻石NV中心)之间的连接已成为控制混合系统中量子信息的有希望的途径。在这个项目中，我们正在努力通过实现一种新型的光学机械系统来扩展这两项努力，该系统能够达到量子区域，同时还可以承载强耦合到光腔的冷分子。我们正在建造的设备也将比现有的光学机械设备更坚固和紧凑。为了实现这些目标，我们正在使用充满超流氦的高精细光学腔。腔体形成在一对光纤之间。精密加工的玻璃套圈被用来对准纤维和遏制超流体。机械元件将是填充在两个纤维之间的超流氦的振动模式。这种设计消除了所有的机械对准，应该会产生非常稳定的设备。数值估计表明，该装置将提供对一系列量子现象的访问，包括观察超流模式的零点运动，压缩光的产生，以及测量光学位移测量的量子反向作用。此外，我们正在探索超流-真空界面的光学力学性质，只在腔内填充部分超流。超流氦可以承载各种类似原子的系统(如亚稳态氦二聚体分子和电子气泡)，这些系统既可以与光学腔相互作用，也可以与氦中的声波相互作用。将光学机械与这种原子状系统相结合，将极大地增强这些设备的通用性。我们正在使用这些超流体光学机械设备来研究测量的量子极限，并产生用于在量子灵敏度极限下运行的仪器的超稳光。这项工作还为研究生提供了激光光学、低温、低噪声测量、信号处理、数据分析和量子光学方面的宝贵培训。这项培训将使他们能够在各种环境中从事基础和应用研究。

The field of optomechanics has progressed rapidly in the past few years from proof-of-principle demonstrations of coupling between optical and mechanical systems to the observation of quantum effects in a handful of these devices. During the same period, connections between optomechanical systems and other AMO systems such as ultracold atoms and diamond NV centers have emerged as promising routes towards controlling quantum information in hybrid systems. In this project, we are working to extend both of these efforts by realizing a new type of optomechanical system capable of reaching the quantum regime while also playing host to cold molecules strongly coupled to an optical cavity. The devices we are building will also be substantially more robust and compact than existing optomechanical devices.To achieve these goals, we are using high finesse optical cavities filled with superfluid helium. The cavities are formed between a pair of optical fibers. Precision-machined glass ferrules are being used to align the fibers and to contain the superfluid. The mechanical element will be the vibrational modes of the superfluid helium filling the space between the two fibers. This design eliminates all mechanical alignments, and should result in a very stable device. Numerical estimates suggest that this device will provide access to a range of quantum phenomena, including observations of the zero-point motion of the superfluid modes, the generation of squeezed light, and measurements of the quantum back action of an optical displacement measurement. In addition, we are exploring the optomechanical properties of superfluid-vacuum interfaces by filling the cavity only partially with superfluid.Superfluid helium can play host to a variety of atom-like systems (such as metastable helium dimer moledules and electron bubbles) that can interact with both the optical cavity and the sound waves in the helium. Combining optomechanics with such atom-like systems would greatly enhance the versatility of these devices. We are using these superfluid optomechanical devices to study the quantum limits of measurements, and to produce ultrastable light for use in instruments operating at the quantum limit of sensitivity. This work is also providing valuable training for graduate students in laser optics, cryogenics, low-noise measurements, signal processing, data analysis, and quantum optics. This training will allow them to pursue basic and applied research in a wide variety of settings.