Full Characterization of a Cavity Electromagnetically Induced Transparency Based Quantum Gate

由于一台实现的量子计算机将产生技术影响，量子信息科学领域是一个备受追捧的研究领域。一个值得信赖的量子处理器的出现将改变科学和工程的许多方面，包括化学反应的优化，超安全通信渠道的开发，以及强大计算机的实体化。经过近二十年的实验研究，已经出现了可以作为量子处理器的基本构件的技术。其中包括与光子和原子相互作用相关的技术。受支持的研究小组旨在开发一个里程碑，以建立量子处理器：实现两个单光子和原子之间的接口，其配置旨在执行量子级别的逻辑操作。这项工作的目标是充分表征一个能够使用光进行两个量子比特操作的原理证明系统。为了实现这一目标，得到支持的研究小组将把量子光学中两个最强大的工具结合在一起；腔量子电动力学(腔QED)用于强光-物质耦合，以及电磁诱导透明(EIT)，以允许控制大的光学非线性。该研究计划将追求两个主要目标。首先，该小组将完成第一个实验装置的构建，在该装置中，两个腔同时耦合到87Rb系综，从而为两个独立的光学模式(量子比特)创造一个相互作用的介质。在EIT条件下，腔场将经历增强的相互作用强度，从而允许使用单光子场来观察非线性效应，单光子场是量子光学门的基本组件。一旦实现，第二个目标是使用一种称为相干态量子过程层析成像(CsQPT)的技术来全面描述门操作。该工具允许仅使用从普通激光光源容易获得的相干态来表征量子光学过程，例如门。

The field of quantum information science is an intensely pursued research area due to the technological impact that a realized quantum computer would have. The availability of a trustworthy quantum processor would revamp numerous aspects of science and engineering, including the optimization of chemical reactions, the development of ultra-secure communication channels, and the materialization of powerful computers. After nearly twenty years of experimental research, technologies have emerged that may serve as the elementary building blocks for a quantum processor. Among these are technologies associated with the interaction of photons and atoms. The supported research group aims to develop a milestone towards building a quantum processor: the realization of an interface between two single photons and atoms in a configuration designed to perform logic operations at the quantum level.The goal of this work is to fully characterize a proof of principle system capable of a two-qubit operation using light. To accomplish this goal the supported research group will interface two of the most powerful tools in quantum optics; that of cavity quantum electrodynamics (cavity QED) for strong light-matter coupling and electromagnetically induced transparency (EIT) to allow control of large optical nonlinearities. The research program will pursue two primary objectives. First, the group will finish construction of the first experimental setup in which two cavities are coupled simultaneously to a 87Rb ensemble, thereby creating an interaction medium for two independent optical modes (qubits). Under EIT conditions, the cavity fields will experience an enhanced interaction strength permitting the observation of nonlinear effects using single-photon fields, the essential component of a quantum optical gate. Once achieved, the second objective is to fully characterize the gate operation using a technique known as coherent state quantum process tomography (csQPT). This tool allows the characterization of quantum optical processes, such as gates, using only coherent states which are readily available from a common laser source.