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Colloquium

22
NOV

Ilias Perakis: Time-resolving superconductivity

2:30pm @ White Hall G09

In solid state materials, quantum states have been mostly manipulated so far by tuning static parameters such as chemical substitution, pressure, electric or magnetic fields.Recently, “sudden” quantum quench and prethermalization have emerged as a cross cutting theme for non-equilibrium manipulation and discovery of emergent quantum states of matter. In this talk, I will discuss how Terahertz (THz) laserpulses can be used to accelerate electrons in a superconducting quantum state during few cycles of electric field oscillations,in a way controlled by electromagnetic propagation effects.By modeling directly in the time domain the transient nonlinear signals observed experimentally, I will demonstrate that THz lightwave driving of supercurrents is a universal dynamical symmetry-breaking principle that allows for observation and control of collective modes in quantum systems. In addition, it can be used to drive new non-equilibrium quantum phases such as long-lived gapless superconductivity. Light-driven Cooper-pair condensate flow during cycles of oscillation manifests itself via high harmonic generation at new frequencies forbidden by the equilibrium symmetry and allows for control of collective modes by THz-pulse shaping. I will also show how the computation of two-dimensional spectra can image quantum states and extract new information from experiments that is not easily accessible with conventional nonlinear spectroscopy.

06
DEC

Curtis Menyuk: Stability and Noise in Frequency Combs: Harnessing the Music of the Spheres

2:30pm @ White Hall G09

Frequency combs have revolutionized the measurement of time and frequency and impacted a wide range of applications spanning basic physics,astrophysics, medicine, and defense. The key theoretical issues in understanding and designing frequency combs are finding regions in the adjustable parameter space where combs operate stably, determining their noise performance, and optimizing them for high power, low noise, and/or large bandwidth. Here, we present a unique set of computational tools that we have developed that allow us to efficiently address these issues. These tools combine 400-year-old dynamical systems theory with modern computational methods, and they are 3–5 orders of magnitude faster than standard evolutionary methods and provide important physical insight. We have applied these tools to frequency combs from passively modelocked lasers with fast and with slow saturable absorbers and to frequency combs from microresonators. Our methods predict improved operating regimes for combs that are produced from both the passively modelocked lasers and the microresonators.