Quantum Communication and Entanglement with Atomic and Optical Systems

在这个项目中，研究人员将进行一系列实验来研究量子通信的物理特性。他们将研究两种传输数据的方法，通过将数据编码到物理对象的量子态上——光场或蒸汽中的原子集合。研究人员将探索使用宏观光脉冲来表示每个数据位。特殊的光压缩状态将用于提高安全性，同时允许精确的编码和读取比特。非线性光放大器将用于产生这些状态。这将是目前使用单个光子存储每个比特的方法的推广。将探讨安全传输数据的方法的相对优点和缺点。在另一种方法中，研究人员将研究一类使用宏观原子集合来表示量子信息的系统。原子系综以一种适合描述为集体谐振子模式的方式被激发，这种模式由玻色自由度表示。因此，连续变量量子信息的概念将发挥作用。这项工作的目标将是通过条件测量来创建集体原子系综变量的量子态，并在两个这样的远距离系综之间创建纠缠。这将为远距离量子通信网络的进一步发展奠定基础。

In this project the investigators will carry out a set of experiments to study the physics of quantum communication. They will study two approaches to transmitting data by encoding it onto the quantum states of physical objects - either light fields or collections of atoms in a vapor. The investigators will explore the use of macroscopic light pulses to represent each data bit. Special squeezed states of light will be used to increase the security while at the same time allowing accurate encoding and reading of the bits. Nonlinear-optical amplifiers will be used to create these states. This will be a generalization of current methods that use single photons to store each bit. Relative advantages and disadvantages of the methods for transmitting data securely will be explored. In the other approach the investigators will study a class of systems that uses a macroscopic ensemble of atoms to represent quantum information. The atomic ensemble is excited in a way that lends itself to a description as a collective harmonic-oscillator mode, represented by a Bosonic degree of freedom. As such, the concepts of continuous-variable quantum information will play a role. The goal of this work will be to create quantum states of collective atomic ensemble variables by conditional measurement and to create entanglement between two such distant ensembles. This will set the stage for further development of quantum communication networks over long distances.