Photons interacting with Rydberg super atoms

在这个项目中，我们研究传播光子与小原子云的相互作用，从而产生所谓的里德伯超原子。其主要思想是，光子将原子基态耦合到一个高度激发的里德伯态，要么是在电磁感应透明的环境中，要么是在中间p能级可以绝热消除的环境中。Rydberg原子之间的强相互作用导致了封锁现象，在小于封锁半径的原子云中抑制了Rydberg态的第二次激发，从而导致Rydberg超原子的形成。S. Hofferberth教授的实验组和H.P. b<e:1> chler教授的理论组合作的主要重点是研究由超原子引起的量子现象及其在量子信息处理中的潜在应用。一个重要的方面是在几个里德伯超原子的传播光子上诱导的相关性：该联盟先前已经成功地观察到单个超原子的行为，通过在出射光场中出现拉比振荡。一个有趣的研究问题是光子与几个超原子相互作用时的行为和相关关系的变化。在理论方面，一个基本问题是是否可以使用量子回归定理来确定相关性。因此，一个主要的目标是推导量子回归定理在这一制度下的有效性，并在实验上探索其有效性或在适当的实验装置中探索修正。另一个重要的方面是单个超原子的电磁诱导透明行为。重点是在这种设置下光子束缚态的出现。在所有这些研究中，超原子的消相是至关重要的，并且可能导致相关性的基本限制，这可以通过实验实现。因此，理论小组将在三维环境中研究光子的虚拟交换行为和减相。最后，我们从理论上研究了里德伯极化子在微观环境下的传播，其中考虑了原子的离散和随机分布。这种方法使我们能够研究反向散射的影响，并提供在EIT环境中光子存储效率的内在界限和实现光子量子门的方案。

In this project, we study the interaction of propagating photons with small atomic clouds giving rise to so-called Rydberg superatoms. The main idea is, that the photons couple the atomic ground state to a highly excited Rydberg state either in a setup with electromagnetic induced transparency or in the regime, where an intermediate p-level can be adiabatically eliminated. The strong interaction between the Rydberg atoms leads to the blockade phenomenon, which suppressed the second excitation of a Rydberg state in an atomic cloud smaller than the blockade radius, and therefore leads to the formation of Rydberg superatoms. The main focus of this collaboration between the experimental group of Prof. S. Hofferberth and the theoretical group of Prof. H.P. Büchler is on the quantum phenomena induced by such superatoms and their potential application for quantum information processing. One important aspect are the correlations induced onto the propagating photons for several Rydberg superatoms: The consortium has previously successfully observed the behavior of a single superatom by the appearance of Rabi oscillations in the outgoing light field. An interesting research question is then on the behavior and the modifications on the correlations for photons interacting with several superatoms. On the theoretical side, a fundamental question is whether the correlations can be determined using the quantum regression theorem. Therefore, a main goal is the derivation of the validity of the quantum regression theorem in this regime and probe experimentally either its validity or probe corrections in a suitable experimental setup. Another important aspect is the behavior of electromagnetic induced transparency for a single superatom. The focus is on the appearance of photonic bound states in such a setup. In all these studies, the dephasing of a superatom is crucial and might lead to a fundamental limit on the correlations, which can be experimental achieved. Therefore, the theory group will study the behavior and the dephasing by virtual exchange of photons in a three-dimensional setting. Finally, we study theoretically the propagation of Rydberg polaritons in a microscopic setting, where the discrete and random distribution of the atoms is taken into account. This approach allows us to study the influence of back scattering as well as provide an intrinsic bound on the efficiency of photon storage in a EIT setting and schemes for realization of photonic quantum gates.