EIT-based quantum light-matter interfaces using ultracold atoms

我们正试图建立一个在量子水平上连接光和原子的系统。量子信息处理承诺的能力超过了当前技术可能实现的任何能力(绝对牢不可破的密码系统，某些算法的指数级计算，等等)，但需要发明新的技术才能实现。量子光(单光子)已经被用于商业原型的安全通信，但将这种系统转变为计算设备将需要某种类型的光子开关，因为如果让它们自己的设备，一束光将平静地穿过另一束，而不会有任何可以用于计算的相互作用。这类技术最有希望的途径之一是使用原子，原子与光相互作用强烈。问题是，到目前为止，观察到的相互作用太弱了数十亿倍，无法让单个量子光(光子)相互切换。最近的提案表明，缩小这一差距是可能的，但这涉及到特殊设计的光源和仔细控制的激光冷却原子。幸运的是，在我们的实验室里，我们已经有了一个由Rb原子组成的“玻色-爱因斯坦凝聚体”(冷却到比绝对零度低得多的百万分之一度)，以及一种我们专门为与Rb相互作用而开发的量子纠缠光的新来源。这项提议将使我们能够获得两种基本的设备，一是以量子逻辑中所需的谨慎方式捕获和操纵原子，二是产生和定制特定的光束，预计这将增强所需的相互作用。这是一个在国际上竞争激烈的研究领域，但我们处于极好的起点，如果我们成功，这种独特的能力将在原子、分子和光学物理领域打开新的大门，特别是在量子信息处理方面。

We are trying to build a system to interface light and atoms at the quantum level. Quantum information processing promises capabilities beyond anything possible with current technology (absolutely unbreakable cryptographic systems, exponentially faster computation of certain algorithms, et cetera), but will require the invention of new techniques to realize. Already, quantum light (single photons) is used in commercial prototypes for secure communication, but turning such systems into computational devices will require some sort of "photon switch," since left to their own devices, one beam of light will placidly pass through another without any kind of interaction which could be used to compute. One of the most promising avenues for such technologies involves the use of atoms, which interact strongly with light. The problem is that so far, the interactions observed have been billions of times too weak to let individual quantum particles of light (photons) switch one another. Recent proposals suggest that it may be possible to close this gap, but this involves specially designed sources of light and carefully controlled laser-cooled atoms. We are fortunate in our lab to already have a "Bose-Einstein condensate" of Rubidium atoms (cooled to well below a millionth of a degree above absolute zero), and a novel source of quantum-entangled light we have developed specifically for interactions with Rubidium. This proposal will allow us to acquire two essential pieces of equipment for trapping and manipulating the atoms in the careful manner required for use in quantum logic, and for generating and tailoring the specific beams of light which are predicted to enhance the desired interaction. This is a highly competitive area of research internationally, but we are in an excellent starting position, and if we succeed, this unique capability will open new doors in atomic, molecular, and optical physics, and particularly for quantum information processing.