Quantum Optics with Polariton Condensates

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Creating Bose condensates of polaritons in microcavity structures is now fairly routine. In addition, we now have structures which have very long polariton lifetime compared to their thermalization time, so that we can do experiments with equilibrated condensates of these particles. This project has three primary goals based on our ability to make long-lifetime polariton condensates. First, we plan to use a polariton condensate to create enhanced two-photon absorption. In principle, this enhancement can be so much that the two-photon absorption process becomes deterministic even for sets of two single photons. This would have immediate impact in the area of quantum optics. The second main goal is to map the phase diagram of an equilibrium polariton condensate as a function of density and temperature, with emphasis on the changes of the spectral function of the condensate, which is immediately observable to us. In addition, we plan to create intersecting beams of ballistic polaritons, which would allow us to do many polariton-polariton scattering studies.Bose condensation is a ubiquitous effect in which many particles spontaneously organize to act collectively as a single wave. The most well known example of this is a gas of atoms at ultra-low temperatures, but the effect occurs in other systems as well. In recent years, it has been shown to occur at moderate temperatures (tens of Kelvin) with particles called "polaritons", which are essentially photons that have been given atom-like properties, namely mass and weak interactions, by means of a specially designed optical system. A main goal of this project is to use a Bose condensate of polaritons to manipulate the transmission of infrared photons. If this goal succeeds, we will have a system in which one photon passing through the system will be unaffected, but two photons passing through together will be absorbed. This ability to manipulate single photons can be used in a number of schemes of quantum optical communications. The project will be tremendous experience for graduate students working on the project to do cutting edge optics research.