HQOC/ITAMP Joint Quantum Sciences Seminar Wednesday, October 3rd, 4:00 PM, J250 Guest Presenter: Prof. Charles S. Adams, Durham University Talk title: Photon-photon interactions using cooperative non-linear optics. Abstract: Ever since the invention of the laser, the field of non-- linear optics has been at the forefront of progress in optical information and communication technologies. However, one area where non--linear optics has been constrained by fundamental physics is the control of photons at the single quanta level. We address this issue using an alternative type of optical non--linearity that is mediated not directly by the interaction between light and matter, but indirectly by the interaction between light--induced excitations, i.e., dipole-dipole interactions. For example, the giant dipoles associated with highly excited Rydberg states can induce a cooperative response of say 1000 neighbouring atoms, thereby greatly amplifying the effect of each photon. In this talk I will present some interesting consequences of this cooperative response including light induced phase transitions and optical bistability. Student Presenter - Emanuele Dalla Torre, ITAMP/Lukin Lab Post Doc "Dissipative Preparation of Spin Squeezed Atomic Ensembles in a Steady State" -- Joan Hamilton Faculty Assistant to Profs. Lukin and Greiner HQOC Administrative Coordinator Harvard University Department of Physics 17 Oxford Street Cambridge, Ma 02138 Phone 617-496-2544 HUCTW Local Representative for the Department of Physics