QnTM: Entanglement in mesoscopic atomic clouds and quantum networking

这项提议的科学目标是演示和研究对建立能够可靠地在宏观距离上传输量子信息的网络至关重要的技术。经过激光冷却并存储在光阱中的中性原子具有低的退相干速率，非常适合以量子比特的形式存储量子信息。为了在宏观上分离的中性原子量子比特之间传输信息，可以将信息映射到由一个原子发射并被接收原子探测到的光子上。由于单个原子具有较小的光子产生和探测截面，我们提出并将演示单个原子与介观多原子量子比特的耦合，然后由介观系综高效地产生光子量子比特。然后，发射的光子被接收系综探测到，接收系综又耦合到单个原子量子比特。将这些元素组合在一起，将实现连接单原子量子比特的量子通道。量子通道可用于传输量子信息和创建可用于隐形传送原子态的远距离钟态。我们的实验方法是基于使用单个原子以及在光学陷阱中以高密度存储的原子系综。原子被激光冷却到几个微开尔文的动能。相干激光技术被用于量子比特操作和强相互作用里德堡态的激发。里德堡态被用来耦合单个原子和多个原子系综之间的信息。用几束激光对系综进行相干操控，可以在所需的方向上产生确定的光子发射。提出的活动的智力价值在于研究和演示了许多粒子的纠缠。纠缠的存在提供了经典和量子现象之间的鲜明区别，并且是量子力学系统计算能力的基础。这项研究将扩展我们创造和利用纠缠来控制信息流的能力，并将展示单原子量子比特与介观量子比特纠缠的可能性。拟议活动的更广泛影响将包括对量子计算和通信技术的发展做出贡献。这些量子力学方法具有前所未有的计算能力，以及安全的信息传输。此外，将在威斯康星大学麦迪逊分校进行的研究将使本科生、研究生和博士后研究人员接触到最先进的技术和工具，并培训他们为社会的技术和科学发展做出贡献。我们一直有本科生大力参与我们关于这一主题的研究，并将在拟议的工作中继续这样做。

The scientific goal of this proposal is to demonstrate and study techniques that will be important for building networks that can reliably transmit quantum information over macroscopic distances. Neutral atoms that have been laser cooled and stored in optical traps have low decoherence rates and are well suited for storing quantum information in the form of qubits. In order to transfer information between macroscopically separated neutral atom qubits the information can be mapped onto photons that are emitted by one atom and detected by the receiving atom. As individual atoms have small cross sections for photon generation and detection we have proposed and will demonstrate coupling of single atoms to mesoscopic many atom qubits, followed by efficient generation of photonic qubits by the mesoscopic ensemble. The emitted photon is then detected by a receiving ensemble, which is in turn coupled to a single atom qubit. Combining these elements will enable a quantum channel that connects single atom qubits. The quantum channel can be used for transmitting quantum information and for creating distant bell states that can be used for teleportation of the atomic states. Our experimental approach is based on using single atoms as well as ensembles of atoms stored at high densities in optical traps. The atoms are laser cooled to kinetic energies of a few micro Kelvins. Coherent laser techniques are used for qubit manipulation as well as excitation of strongly interacting Rydberg states. The Rydberg states are used to couple information between single atoms and many atom ensembles. Coherent manipulation of the ensembles with several laser beams results in deterministic emission of photons in a desired direction. The intellectual merit of the proposed activity is in the study and demonstration of many particle entanglement. The presence of entanglement provides a sharp distinction between classical and quantum phenomena, and is fundamental to the computational power of quantum mechanical systems. This research will extend our ability to create and harness entanglement for controlling the flow of information and will demonstrate the possibility of entangling single atom qubits with mesocopic qubits.The broader impact of the proposed activity will include contributions to the development of quantum techniques for computing and communication. These quantum mechanical approaches have the potential for unprecedented computational power, as well as secure transmission of information. In addition the research to be performed at The University of Wisconsin - Madison will expose undergraduate students, graduate students, and postdoctoral researchers to state of the art techniques and tools, and train them to contribute to the technological and scientific development of society. We have consistently had strong involvement of undergraduate students in our research on this topic and will continue to do so in the proposed work.