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Colloquia are Wednesdays at 4:00 p.m. in the JILA Auditorium.Ìý

Coffee, tea and cookies will be available in G1B31 (across from G1B20) from 3:30 - 3:50 p.m.

August 27 — "Quantum Simulation and Sensing with Atoms Interacting via Photons"

• Presenter: James K. Thompson, JILA, ÌÒÉ«ÊÓƵ
• Host: Ana Maria Rey
• Abstract: Photons bouncing back and forth many times between mirrors provide a way for atoms to interact at essentially infinite range. ÌýThese interactions open powerful new paths for quantum simulation and quantum sensing, allowing us to leverage the certainty provided by quantum mechanics to make very precise measurements of the world around us, or allowing us to emulate one quantum system with another to provide insights and understanding. In this talk, I will provide a sampling of my group’s work including how we use the quantum measurement process and interactions to create some of the most highly-entangled states realized in any system, realize the first entanglement-enhanced matterwave interferometer, and simulate the predicted dynamical phases of BCS superconductors.

*Colloquium Canceled* September 3

*Colloquium Canceled* September 10

September 17 — "Machine Protection for the Large Hadron Collider and Beyond"

• Presenter: Christoph Wiesner, Machine Protection and Electrical Integrity Group (MPE), CERN, Geneva, Switzerland
• Host: Mihaly Horanyi
• Abstract: The Large Hadron Collider (LHC) at CERN is the most powerful particle accelerator ever constructed. It enables the study of the fundamental structure of matter by providing proton-proton collisions at the unprecedented energy of 6.8 TeV per beam. It delivers an instantaneous luminosity exceeding 2×10³⁴ c³¾^−2s^−1 at its two general-purpose detectors, ATLAS and CMS. During high-intensity operation, the LHC now routinely stores energies of 430 MJ per beam—well beyond its original design specifications.
  Given the high energies stored in both its particle beams and superconducting magnet circuits, the LHC requires a sophisticated machine protection system. This presentation will outline the key challenges and describe the main elements of the LHC machine protection system. Examples of relevant beam loss scenarios, including interactions between the particle beam and dust contaminants, will be presented. Finally, an outlook for future high-intensity colliders will be given.

September 24 — "Listening to the Universe above the quantum din"

• Presenter: Nergis Mavalvala, Massachusetts Institute of Technology
• Host: Ana Maria Rey
• Abstract: The Laser Interferometer Gravitational-wave Observatory (LIGO) detected gravitational waves for the first time in 2015. Since then, hundreds more astrophysical observations have been confirmed. To detect these spacetime ripples requires measurement with sub-attometer precision. I will describe theÌýquantumÌýtechnologies that make such a measurement possible, enabling present and future discoveries.

October 1 — "Historical trends in atmospheric humidity over arid and semi-arid regions"

• Presenter: Isla Simpson, NSF NCAR
• Host: Ivy Tan
• Abstract: An expected consequence of a warming atmosphere is that atmospheric humidity would rise as a result of the dependency of the atmospheric water vapor holding capacity on temperature (the Clausius-Clapeyron relationship). ÌýBut this is only true if there is sufficient availability of water to satisfy the rising atmospheric demand. ÌýGiven the important implications of atmospheric water vapor content for wildfire and as a general indicator of how the hydroclimate is changing, it is important to ensure that the Earth System Models used for climate projections are accurately representing the historical evolution of atmospheric water vapor. ÌýHere, it will be demonstrated that, contrary to expectations, and to the behavior of Earth System Models, atmospheric water vapor over arid and semi-arid regions in observation-based data has not risen. While Earth System Models suggest that atmospheric water vapor should have risen at approximately Clausius-Clapeyron scaling, atmospheric water vapor in these regions in reality has actually remained relatively constant, raising the possibility that Earth System Models are mis-representing processes of relevance to the hydroclimate. ÌýOngoing work to identify the underlying causes of this discrepancy will be discussed including whether models accurately represent evaporative regimes in day-to-day variability and the potential role for inhomogeneities in the observational record. ÌýÌý
  Isla Simpson is a climate scientist in the Climate and Global Dynamics Laboratory of the NSF National Center for Atmospheric Research.Ìý She obtained her PhD in 2009 from Imperial College London and followed this with postdoc positions at the University of Toronto and Lamont-Doherty Earth Observatory, Columbia University, before joining NSF NCAR in 2015.Ìý At NSF NCAR, Isla works on assessing the representation of processes in Earth System Models and in using these models to understand long-term climate trends and predictability of the Earth System.Ìý She leads the Climate Analysis Section, is co-chair of the Community Earth System Model Climate Variability and Change Working Group and is co-chief editor of the Journal of Climate.

October 8

• Presenter: Ike Chuang, Massachusetts Institute of Technology
• Host: Ana Maria Rey
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October 15

• Presenter: Merav Opher, Boston University
• Host: Mihaly Horanyi
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October 22

• Presenter: Minhyea Lee, ÌÒÉ«ÊÓƵ
• Host: Tobin Munsat
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October 29

• Presenter: Longji Cui, Mechanical Engineering, ÌÒÉ«ÊÓƵ
• Host: Gang Cao
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November 5

• Presenter: Scott Lawrence, Los Alamos National Laboratory
• Host: Ethan Neil
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November 12

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November 19

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November 26 — No Colloquium, Fall Break

December 3

• Presenter: Eric Braaten, Ohio State University
• Host: Tom DeGrand
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For more information about colloquia this semester, contact: Mike Litos