Strongly interacting single photons in an ultra-cold Rydberg gas

强光子-光子耦合原则上可以在极端非线性介质中实现。对少光子非线性的研究是一个非常活跃的领域，包括量子点、金刚石中的NV中心、原子系综和光学谐振器中的单原子等各种系统。然而，到目前为止，还没有实现例如单光子开关的鲁棒和可扩展的实现。在这个项目中，我们将实现一种新的方法，通过将超冷气体中强相互作用原子之间的量子相关映射到单个光子上，来显著增强光子-光子相互作用。利用电磁感应透明（EIT）将光子相干转换为里德伯原子，利用高激发态原子间的强相互作用在单光子水平上实现光的操纵。这种光的量子态与强关联量子介质之间的界面，开辟了一个超越经典非线性光学的全新研究领域。在这个项目的过程中，我们将使用这种技术来实现光子量子信息处理的基本构建模块，例如确定性单光子源和量子相位门。此外，我们将把我们的相互作用光子系统应用于强关联多体系统的研究，实现一种用量子光学工具模拟复杂多体哈密顿量的独特方法。

Strong photon-photon coupling can in principle be achieved inside extremely nonlinear media. The search for few-photon nonlinearities is a highly active field, including such diverse systems as quantum dots, NV centers in diamond, atomic ensembles, and single atoms in optical resonators. However, no robust and scalable realization of, for example, a single-photon switch has been achieved so far. In this project we will realize a novel method for dramatically enhancing photon-photon interactions by mapping quantum correlations between strongly interacting atoms inside an ultra-cold gas onto single photons. Using electromagnetically induced transparency (EIT) to coherently convert photons into Rydberg atoms, we will exploit the strong atom-atom interaction between highly excited atoms to manipulate light on the single-photon level. This interface between quantum states of light and strongly correlated quantum media opens a completely new research field beyond classical nonlinear optics. In the course of this project we will use this technique to implement fundamental building blocks for photonic quantum information processing, such as a deterministic single-photon source and a quantum phase gate. Furthermore, we will apply our system of interacting photons to the study of strongly correlated many-body systems, realizing a unique approach of simulating complex many-body Hamiltonians with quantum optics tools.