Atom-Photon Entanglement and Functional Quantum Network Nodes with Atomic Ensembles

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The development of quantum mechanical approaches to processing, storage, and transmission of information is being actively pursued around the world. Quantum processors are distinct from existing classical systems in that they harness unique features of quantum physics to enable beyond classical capabilities. These include the potential for efficiently solving currently intractable computational problems, for simulating complex physical systems in order to develop new materials, and the ability to transmit information securely between distant locations. One of the approaches being actively pursued is to use quantum bits (qubits) stored in neutral atoms for memory and processing and to use optical photons (particles of light) for long distance transmission of information. A necessary step is entanglement, that is where a single particle of light, a photon, and/or an atom can be correlated with another photon or another atom such that measuring the properties of one instantaneously affects the properties of the other even if they are not in the same location. While entanglement between atoms and photons has been demonstrated in many experiments what has not yet been achieved is the ability to combine atom-photon entanglement with atomic qubits that can process and store information. The major goal of this research is to demonstrate atom-photon entanglement and atom based quantum logic gates in a single system that can form the basis for future quantum networks. The research program will also contribute to the training of students for careers in science and engineering. People from diverse backgrounds will be educated and trained in modern experimental science, and will be equipped to bridge the boundary between physics and information science. Training will occur via curriculum enrichments, and through direct participation in the University based research program. We will also inform the local Madison community about the importance of physics to information technology, and the new developments in the area of quantum information science. Outreach to the public will be facilitated by public visiting days at the Physics department, laboratory tours, faculty visits to local schools, and mentoring of high school students.Our technical approach is based on the use of small clouds of atoms with from 10-100 Rubidium atoms for the dual purpose of creating entanglement between atoms and photons, and as qubits in a small quantum processor. We will use long range interactions mediated by highly excited Rydberg states of atoms to create deterministic entanglement between qubits encoded in multi-atom ensembles and between ensembles and light. These capabilities will form the basis for efficient quantum repeater architectures needed for long distance distribution of entanglement and quantum networking.