Nonlinear Optics in the Quantum Regime, Based on Ultracold Rydberg Atoms

光学本身就是物理研究的核心领域，它继续产生新技术，这些技术在从原子物理到信息科学再到生物和医学等领域得到广泛和极其强大的应用。过去50年来，大多数现代光学研究大致分为两个领域：“非线性光学”，强光之间的相互作用导致丰富、复杂的现象；以及“量子光学”，光的粒子性质发挥作用，量子力学产生的新效应已被证明提供了令人兴奋的新可能性(例如，用于超安全通信、某些计算任务的指数加速，以及量子增强的精度测量)。这种“非线性”相互作用通常很弱，以至于在单光子水平上是看不到的，这意味着这两个光学物理领域朝着相反的方向移动，几乎没有重叠。基于最近的一项发现，即高激发原子态(称为里德堡态)可以用来在单光子水平上产生强大的相互作用，将这两个领域结合起来突然变得可行，开发了一个以前无法进入的本质上新的物理学领域。在这一“量子非线性光学”的新前沿，将利用丰富的非线性相互作用来创造和利用量子纠缠。除了为基础研究开辟一个全新的领域外，这还有望带来强大的新量子技术，例如用于量子计算和模拟的新技术。我们正在申请资金来购买激发这些里德伯格态所需的激光系统，这是基于我们小组在超冷原子和纠缠光子方面的独特专业知识组合，以及我们几年来关于量子光物质接口的项目。这种设备将使我们成为世界上参与这一新物理领域诞生的少数几个团队之一。

Optics, a central field of physics research in its own right, continues to produce new technologies which find widespread and extremely powerful application in fields ranging from atomic physics to information sciences to biology and medicine. Most of modern optics research over the past 50 years falls broadly into two areas: "nonlinear optics," where interactions between intense beams of light lead to rich, complex phenomena; and "quantum optics," where the particle nature of light plays a role and novel effects due to quantum mechanics have been shown to offer exciting new possibilities (e.g. for ultrasecure communications, exponential speedups in certain computational tasks, and quantum-enhanced precision measurement). Such "nonlinear" interactions are generally so weak that they are unobservable at the single-photon level, meaning that these two realms of optical physics have moved in opposite directions, with very little overlap. Based on the recent discovery that highly excited atomic states (known as "Rydberg states") can be used to generate powerful interactions at the single-photon level, it is suddenly becoming feasible to merge these two areas, developing an essentially new field of physics, previously inaccessible. In this new frontier of "quantum nonlinear optics," the richness of nonlinear interactions will be harnessed to create and utilize quantum entanglement. In addition to opening up an entirely new domain for fundamental research, this has the promise to lead to powerful new quantum technologies, for instance for quantum computation and simulation. We are requesting funds to purchase the laser systems necessary to excite these Rydberg states, building on our group's unique combination of expertise with ultracold atoms and entangled photons, along with our several-year-old project on quantum light-matter interfaces. This equipment will position us to be among the handful of teams around the world participating in the birth of this new field of physics.