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Two-Part Seminar: "Effective Field Theory" AND "Frontiers of Photon Counting"

November 7, 2016 - 11:00am
Michael Gullans & Ivan Burenkov
Note: Each presentation is allocated 25 minutes plus 5 minutes for discussion.
Pt. 1: Effective Field Theory for Strongly Correlated Photonic Matter
Speaker: Michael Gullans
A promising route to scaling up quantum information systems is to strongly couple light, or other propagating quantum fields, to localized electronic degrees of freedom in solids or trapped atoms.  Describing the emergent non-equilibrium behavior of such strongly coupled light and matter is an outstanding challenge for theoretical physics and quantum information science.  A simplifying feature of these systems, however, is that they are often characterized by a large separation of scales between the atomic and photonic degrees of freedom.  In this talk, I will discuss recent results where we took advantage of this separation of scales to develop an effective field theory description of interacting photons in cold gases of Rydberg atoms, where the photons become dressed with highly excited Rydberg states.  This theoretical approach is analogous to semiclassical nonlinear optics, where the electronic degrees of freedom are integrated out to give rise to effective photon-photon interactions.  As an application of this theory, I will show how such Rydberg polariton systems may provide new insights into universality in few-body quantum systems. 
Pt. 2: Frontiers of Photon Counting: From Quantum Mesoscopic States To Ultra-Low Intensities
Speaker: Ivan Burenkov
Responding to the needs of practical quantum information processing much effort is directed towards engineering and characterizing a suite of scalable and hybrid quantum tools. We combine the latest advances in source engineering, detector development, and advanced measurement techniques to reconstruct the mode structure and optical losses of multimode mesoscopic optical fields using an experimentally measured joint photon-number probability distribution. We also characterize an efficient and inherently ultra-low noise frequency conversion via a parametric sum frequency generation. This upconverter generates only 100 background photons per hour. To measure such a low rate, we introduced a dark count reduction for a transition edge sensor.
CSS 2400, MD 20742