Past Events

Integrated quantum photonic and acoustic sensors

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Abstract: Integrated sensors have fundamentally revolutionized nearly all electronic systems. How can quantum technology contribute? In this talk, I aim to present recent advances in integrated quantum nonlinear photonics and electromechanics and outline their potential to enhance sensing technologies. I'll start by presenting Stokowski [1] and Park's [2] demonstrations of integrated quantum optical sensors and squeezed light sources in thin-film lithium niobate.

Pulsar Timing Arrays: A New Window on the Gravitational Wave Universe

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Abstract:

Millisecond pulsars are rapidly rotating neutron stars with phenomenal rotational stability. Pulsar timing arrays world-wide monitor over 100 of these cosmic clocks in order to search for perturbations due to gravitational waves at nanohertz frequencies. The tell-tale sign of a stochastic background ofgravitational waves in pulsar timing data is the presence of quadrupolar spatial correlations.

Photon upconversion: getting molecules and nanocrystals to talk triplets

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Abstract: In order to harness the intrinsic ability of colloidal semiconductor nanocrystals to couple strongly with light, it is important to efficiently outcouple energy from photoexcited quantum dots (QDs), much like how nature uses molecular antennas to direct light during photosynthesis. This talk focuses on aromatic acceptor ligands for triplet-fusion based photon upconversion, where orbital overlap between the QD donor and molecular acceptor is critical for efficient energy transduction.

Symmetry, topology and electronic phases of matter

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Abstract: Symmetry and topology are two of the conceptual pillars that underlie our understanding of matter. While both ideas are old, over the past several years a new appreciation of their interplay has led to dramatic progress in our understanding of topological electronic materials. A paradigm that has emerged is that insulating electronic states with an energy gap fall into distinct topological classes. Interfaces between different topological phases exhibit gapless conducting states that are protected and are impossible to get rid of.

Chemical Kinetics in Microdroplets

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Abstract: Over that last 10+ years there has emerged some evidence that when a reaction vessel is reduced to the micron-sized dimensions (e.g. droplets), bimolecular reactions speed up by many orders of magnitude. The mechanism(s) for rate acceleration in droplets remains unclear but has clear implications for understanding the chemistry of atmospheric aerosols. A key uncertainty in the interpretation of droplet kinetics is how to properly link reaction rates measured in beaker scale containers with those occurring in micron-sized spaces.

Nonlinear effects in magnetic systems: from nano to macro scales

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Abstract: Wave interactions are responsible for the various aspects of the behavior of different systems in nature, including processes in the oceans and atmosphere, star hydrodynamics, and even the evolution of the Universe. Spin waves (and their quanta–magnons) in magnetically ordered materials are highly nonlinear compared to, for example, phonons or photons in solids.

Waves of Topological Origin in the Fluid Earth System and Beyond

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Abstract: Symmetries and topology are central to our understanding of physical systems. Topology, for instance, explains the precise quantization of the Hall effect and the protection of surface states in topological insulators against scattering from disorder or bumps. However discrete symmetries and topology have not, until recently, contributed much to our understanding of the fluid dynamics of oceans and atmospheres.

Extreme Ultraviolet Spectroscopy of Ultrafast Excitations in Magnetic Alloys

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The next generation of logic devices may rely on very fast switching of magnetic states. In this thesis, I utilize ultrafast pulsed lasers to measure and manipulate magnetic states on their fundamental timescales: ranging from few-femtoseconds spin-transfers in Heusler alloys to magnetization reorientations in ferrimagnets which take tens of picoseconds. I utilize high harmonic generation to produce a tabletop extreme ultraviolet probe for resonant measurements.