Rydberg units interfaced: Coherence and Entanglement

相干和纠缠是量子系统的基本性质，它们通过与环境的耦合而逐渐丧失。研究如何在空间上传输纠缠以及如何保护相干性已经引起了人们的极大兴趣，特别是在量子信息处理中，其中的读入和读出步骤强制将纠缠的量子系统与不可避免地导致退相干的环境相连接。另一方面，系统的研究如何连接一个有限的量子系统与另一个（或与经典系统）动态地改变其相干特性是稀缺的。一个原因可能是很难找到实验测试系统，允许调整这些一致性属性。具有"超原子“和聚集体的超冷里德伯气体可以被设计成具有明确定义的相干程度，从而缓解这种情况。（微米）和时间（微秒）尺度允许人们以受控的方式将这些里德伯量子系统与环境连接起来，使得可以相对容易地监控相干和纠缠特性的最终变化。因此，与许多先前的设置相比，我们希望能够提取和理解相干性和纠缠损失的相关机制。在这个提议中，我们将采取第一步，并并行研究两个相互补充的方案：第一个是接口两个里德伯单元，我们指的是里德伯激发原子在受控位置和受控环境的组装。虽然这种情况是完全对称的，系统和环境的作用可以交换，但第二种情况被故意选择为非常不对称：我们通过将超冷的里德伯气体耦合到机械纳米级镜子来创建一个光学机械系统，激光穿过里德伯云并从镜子反射。改变激光器参数允许在这里和外部控制相干性。

Coherence and entanglement are fundamental properties of quantum systems which are gradually lost through coupling to the environment. Investigations how to spatially transport entanglement and how to protect coherence have attracted considerable interest, particularly in quantum information processing where the read-in and read-out steps enforce to interface the entangled quantum system with an environment leading inevitably to decoherence. On the other hand, systematic studies how interfacing a finite quantum system with another one (or with a classical system) dynamically changes its coherence properties are scarce. A reason may be the difficulty to find experimental test systems that allow tuning these coherence properties. Ultracold Rydberg gases, with ``superatoms'' and aggregates can be designed to have a well defined degree of coherence and thus alleviate this situation.It is the aim of this proposal to show that their spatial (micrometer) and temporal (microsecond) scale allows one to interface these Rydberg-quantum-systems in a controlled way with an environment, such that the resulting change of coherence and entanglement properties can be monitored with relative ease. Thus, in contrast to many prior setups, we expect to be able to extract and understand the relevant mechanisms of loss of coherence and entanglement. Within this proposal we will take the first step and investigate in parallel two scenarios which supplement each other: The first one is to interface two Rydberg units, by which we refer to an assembly of Rydberg excited atoms at controlled positions and with controlled environment. While this scenario is completely symmetric and the role of system and environment can be exchanged, the second scenario is deliberately chosen to be very asymmetric: we create an optomechanical system by coupling an ultra cold Rydberg gas to a mechanical, nano-scale mirror with laser light passing through the Rydberg cloud and being reflected from the mirror. Changing the laser parameters allows here and external control of coherence properties.