The general theme of this project is to investigate methods to create, distribute, and store quantum mechanical states by exploring entanglement between light and matter with ensembles of ultracold atoms. Entanglement, one of the most striking features of quantum mechanics, leads to strong correlations between separate components of a physical system, regardless of the distance separating them. The first specific goal of the project is to develop methods of creating robust entanglement between light and matter with ensembles of ultracold atoms. This project builds upon previously realized entanglement of mixed species atomic "quantum bits" (called qubits) and frequency-encoded photonic qubits. The approach avoids the use of two interferometrically separate paths for qubit entanglement distribution. The second goal is to realize matter-light entanglement at telecommunications wavelengths as an enabling technology to distribute and store entanglement over long distances. The final component of the program involves investigations of dynamics of the entangled systems subjected to continuous measurement.
Achieving these goals should significantly develop atomic physics-based methods for the processing of quantum information. The program involves extensive undergraduate and graduate student training and participation in technologically important areas of physics. The project will include outreach to the Atlanta community through laboratory tours and summer workshops for local high-school teachers.
The award supported work on advancing the state of the art in quantum information processing with cold trapped neutral atoms, and the initiation of a program to trap and laser cool triply charged Thorium. Major results of this work include: 1) Increased quantum memory time by more than two orders of magnitude, in excess of 6 milliseconds. 2) Multiplexing of a dozen quantum memory elements into a cold atomic sample. 3) Increased memory time for atom-light entanglement in excess of 3 milliseconds. 4) Implementation of continuous quantum measurement of the matter-light system. 5) Proposal of two-photon laser compensation of Stark hyperfine broadening for cold trapped atoms. Experimental implementation of this scheme resulted in quantum memory times in excess of 0.1 second. 6) Investigation of magnetic compensation of Stark hyperfine shifts. Using this method, storage of coherent light for longer than 0.3 second was observed, and storage of spin-wave qubit for longer than 0.1 second. 7) Realization of low-noise, high-efficiency wavelength conversion between telecom and near-infrared light. Entanglement of long-lived memories and telecom light. 8) First realization of laser cooling of a multiply charged ion - triply charged 232-Thorium. 9) Proposal for fast generation of atom-light entanglement based on decoherence of Rydberg level spin-waves. Graduate, undergraduate, and postdoctoral students have been trained in areas of atomic, molecular, and optical physics relevant to national technological interests.
