Fundamental Quantum Optics in Hollow-Core Photonic Crystal Fibers

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This program aims to develop a near-ideal material medium for generating and manipulating nonclassical states of light for fundamental studies in quantum information science. By ideal we mean photon-atom interactions in a system having isolated degrees of freedom that may evolve to become entangled among themselves without becoming entangled to any reservoir of unmonitored auxiliary systems. The system being developed is comprised of ultrahigh-density xenon gas confined to the interior of a hollow-core photonic crystal fiber (PCF), which can guide tightly focused light over several meters, enhancing the light-matter interaction. This system combines several outstanding properties, making it ideal for use as a medium for four-wave mixing interactions between light beams, including photon pair generation, mode entanglement, optical frequency comb generation, and soliton propagation. Being a fluid (at temperature 16 C and pressure 57 bar), near-critical Xe has variable density like a gas, but at the same time has a very high third-order optical nonlinearity -- approaching that of solid silica glass, which is the standard fiber-based medium now in wide use. Being an atomic gas, Xe has negligible levels of Raman and Brillouin scattering, which are severe impediments to current studies using silica as a nonlinear-optical medium. In the high-density Xe system we expect to see reduced noise signals and enhanced entanglement in photon generation, and reduced noise and enhanced quantum squeezing in frequency comb generation and soliton propagation, enabling deeper fundamental studies of these phenomena. Challenges include designing Xe-filled PCF to have the needed dispersion properties for phase matching the nonlinear-optical processes of interest. Such a new medium could find widespread use in the optical quantum-information community, and could transform our abilities to perform all-optical quantum-state generation and manipulation tasks.Quantum information technology aims to create, store, transmit, and process information in ways not possible using classical-physics-based techniques. For this we need "ideal interactions" between light and matter, with which to transfer information between two physical systems without having that information partially "leak" into the surroundings. Such leakage would destroy the quantum "integrity" of the systems (atoms or photons) being used to store and process the quantum information. Such ideal interactions are at the heart of proposed quantum optical technologies, such as secure long-distance communication and quantum computing using photon states. In order for such technologies to become useful, we need nearly ideal methods to prepare, control, and manipulate quantum states of photons and optical fields.For this purpose we are developing a unique optical material system -- high-density xenon gas confined to the interior of a hollow-core optical fiber -- which can guide tightly focused light over several meters, enhancing the light-matter interaction. Such a system is projected to enhance the interaction of light with xenon gas -- the most highly interacting of the nobel gases -- by several orders of magnitude compared with room-pressure gas in a standard gas cell. When intense laser light passes through such a gas, its frequency spectrum can be altered in a predictable way, generating many new frequencies, while maintaining the "integrity" of the quantum state of the light. This offers the possibility to create "quantum-entangled" states of many light waves having different frequencies. This interaction can also create quantum solitons, which are light pulses that travel in the xenon gas without becoming stretched in time, as usually occurs when light pulses propagate. Studying solitons can provide tests of the most sophisticated quantum field theories for describing the light-mater interaction.Quantum optics offers excellent opportunities to integrate research with science education. PhD students currently involved in the PI's research have contributed to the NSF's GK-12 Program, which pairs PhD students with high schools and middle schools, exposing their students to the idea of research as a career. High-school students, undergraduate students, Masters and PhD students, as well as visiting scientists, have all been involved in the groups' research in recent years. Students also participate as co-instructors of courses in a new Science Literacy Program at the University of Oregon, co-directed by the PI.