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.
