Fall 2023 Colloquia

Mechanical Sensors for Dark Matter and Neutrinos

Abstract: The development of optomechanical systems has revolutionized the detection of tiny forces over the past few decades. As such technologies reach (and surpass) quantum measurement limits, they can enable new searches for weakly coupled phenomena, including dark matter, gravitational waves, “fifth’’ forces, and sterile neutrinos. As a demonstration of these techniques, I will describe an initial search for dark matter using an optically levitated nanogram mass sensor, which can exceed the sensitivity of even large underground detectors for certain classes of dark matter candidates in a few days of exposure. If a signal were detected, such sensors would also be able to correlate its direction with earth’s motion through the galaxy, allowing definitive confirmation that such a signal arose from dark matter. Finally, I will briefly discuss future applications of such sensors to neutrino physics in a table-top scale experiment.

Precision Spectroscopy of Atomic Hydrogen

Abstract: Because of atomic hydrogen’s simplicity, its energy levels can be precisely described by theory. This has made hydrogen an important atom in the development of quantum mechanics and quantum electrodynamics (QED). While one can use hydrogen spectroscopy to determine the Rydberg constant and the proton charge radius, a discrepancy of these constants determined through different transitions, or in different species, can indicate new physics. Such discrepancies currently persist between different measurements in hydrogen and muonic hydrogen. With this motivation in mind, I will discuss several precision spectroscopy measurements of hydrogen as Colorado State University including a relatively recent measurement of the hydrogen 2S-8D two-photon transition, a measurement of the hydrogen 2S hyperfine splitting, and our future plans to measure several relatively narrow 2S-nS transitions in hydrogen. If these latter measurements are successful, they could provide some of the most precise measurements of the Rydberg constant along with insight into the experimental discrepancies.

October 17, 2023 – NO PHYSICS COLLOQUIUM-FALL BREAK

Quantum State Measurement via Common-Path Interferometry with Entangled Modes

Abstract: Entangled photons are a valuable resource for quantum logic, imaging, and information theory. While measuring entangled state amplitudes is relatively straightforward with coincidence-based correlation filters, the entangled state phases have received relatively little attention – despite the important role that phases play in defining and altering quantum states. In contrast to classical light, for which phase can be easily measured using interference with an ancillary reference beam, the reliance of coincidence detection for biphoton measurements makes it unclear how to implement the requisite reference. Furthermore, phase measurement of entangled states is not as simple as combining separate phase measurements of signal and idler photons, or of interfering them together. In short, a phase-measurement counterpart to direct amplitude measurements has remained elusive. I will show a method to directly measure the phase of biphoton states that uses the broader entanglement spectrum as a resource for interferometry. The technique is demonstrated with entangled photonic spatial modes in the Laguerre-Gaussian basis, and it is applicable to any quantum system that has multiple orthogonal modes. Two different implementations are demonstrated with measurements on entangled photons: a simple version that works in the case of a particular sparse entanglement spectrum, and another that works for general entangled states (including polarization entanglement). As one particularly useful application, we use the new methodology to directly measure the geometric phase accumulation of entangled photons.

Biography: Dr. Mark Siemens is a Professor in the Department of Physics and Astronomy at the University of Denver (DU). His research group uses lasers to characterizes quantum dynamics in materials, and in the lasers themselves. He is the faculty advisor for DU’s Society of Physics Students, which is widely recognized for their physics outreach. 

Title to be announced

Title to be announced

Quantum Regimes of Coherent X-ray Generation with Strongly Correlated Electron Dynamics and Attosecond Rabi Oscillations for Advanced Nanoimaging

Title to be announced

August 22, 2023 – NO PHYSICS COLLOQUIUM

Thomas Fix
University of Strasbourg, ICube Laboratory

New concepts and emergent materials for optoelectronics and photovoltaics

Abstract: This seminar will give an overview of three different topics currently investigated in the Materials for electronic and photovoltaic devices team (MaCEPV) of ICube laboratory.

• Downshifting and downconversion for solar cells

Downshifting and downconversion are advanced concepts for solar cells enabling a better match between the solar cells and the solar spectrum. It consists in the conversion of one ultraviolet photon into one (downshifting) or two (downconversion) photons in the visible or near-infrared.

[a] Photon Converters for Photovoltaics, A. Nonat, T. Fix, in Advanced micro- and nanomaterials for photovoltaics, Elsevier 2019, ISBN: 978-0-12-814501-2

• Oxide solar cells and ferroelectric solar cells

Our team has been developing emergent oxide materials as absorbers for solar cells. In particular, we focused in ferroelectric oxide solar cells where no pn junction is necessary and the separation of electron hole pairs is enabled by the ferroelectric polarization of the absorber.

[b] R. Hoye, J. Hidalgo, R. Jagt, J.-P. Correa-Baena, T. Fix, J. MacManus-Driscoll, Advanced Energy Materials, 2100499, pages 1-59 (2021)

• Silicon clathrate films for optoelectronic applications

Silicon clathrates are exotic forms of silicon, forming cages, that present the advantage of a direct and adjustable bandgap. Our team is one of the three actors in the world producing such films.

[c] T. Fix, R. Vollondat, A. Ameur, S. Roques, J.-L. Rehspringer, C. Chevalier, D. Muller, and A. Slaoui, J. Phys. Chem. C 124, 14972–14977 (2020)

Thomas Fix is a CNRS researcher in the ICube laboratory, University of Strasbourg – CNRS. He obtained his PhD in physics in 2006 at IPCMS and worked for six years as a research associate at the University of Cambridge, UK. His field is advanced concepts and innovative materials for optoelectronics and solar cells.

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September 5, 2023 – PHYSICS COLLOQUIUM-HAZARDOUS WASTE GENERATOR TRAINING REFRESHER

September 12, 2023 – NO PHYSICS COLLOQUIUM-CAREER DAY

Extreme Universe on a Super Pressure Balloon 2: Mission, Science, and Adventure

Abstract: Abstract: Ultra-high energy cosmic rays are the highest energy subatomic particles known to exist. Although much harder to detect, very high-energy neutrinos also carry information about the most extreme environments in the universe. And since they have zero charge, they point back to their creation point. The Extreme Universe Space Observatory on a Super Pressure Balloon II (EUSO-SPB2) was designed to search for PeV energy neutrinos from steady-state and transient astrophysical sources and to measure PeV and EeV cosmic rays using optical techniques from sub-orbital altitude. This exploratory mission of opportunity was a pathfinder for a space observatory such as the Probe of Extreme Multi Messenger Astrophysics (POEMMA). EUSO-SPB2 flew two astroparticle telescopes that featured wide fields of view, 1 meter diameter entrance pupils, and specialized camera systems to measure fast pulses of light from extensive air showers in the atmosphere. A fluorescence telescope was pointed down to measure scintillation light from EeV cosmic ray interactions. A Cherenkov telescope was pointed toward the earth’s limb. This instrument could be tilted a few degrees above the limb to observe Cherenkov emission from PeV energy cosmic rays or tilted below the limb to search for Cherenkov emission from air showers induced through neutrino interactions in the earth’s limb. The gondola could be rotated in azimuth to point the CT to observe sources of interest just before they rise or just after they set. After several years of preparations, lab tests, field tests, reviews, and integrations, the payload was delivered to NASA’s mid-latitude launch site in Wanaka NZ, and launched May 13, 2023. Unfortunately, the balloon developed a bad leak and the entire flight train was terminated into the Pacific Ocean after just two nights aloft. Despite all this, the instruments turned on successfully and worked, with almost 60 GB of data downloaded. Data analysis is in progress with some performance and preliminary results reported at conferences this summer. Planning for a follow-up mission is in progress.

Biography: Grew up in Vermont. AB Dartmouth College, MA, MPhil, PhD Columbia University (I don’t know why they hand out 3 degrees). Did particle physics as a grad student working on an experiment at the historic Alternating Gradient Synchrotron at Brookhaven National Labs. Thesis “Observation of Coulomb Effects in pp and np collisions at 27.5 GeV/c”. By the time I finished my PhD, I needed a change from accelerator laboratories (the uncertainty in accelerator scheduling was interfering with my climbing trips, among other things). Left the NYC area for a postdoc with the High Resolution Fly’s Eye Comic Ray experiment in the Utah West Desert (the HiRes schedule was driven by the moon). Discovered the rewards of working with UV laser systems in the desert, and mountain trail running, and telemark skiing. We made the first observation of high energy cosmic air showers in stereo with the fluorescence technique And made the first observation of the cosmic ray flux suppression around 10^20 eV, explained at that time by energy loss in the cosmic microwave background radiation. While at Utah, I joined the Pierre Auger Observatory project as construction was starting near Malargue, Argentina. I worked with a small team that designed and built a laser system in the middle of nowhere to mimic the optical signatures of high energy cosmic rays, but traveling in the wrong direction. By the time I joined the faculty at Mines in 2007, we had a second of these systems installed in the Pampas. A few months after arriving in Golden it blew up in a massive propane “anomaly”. Despite that, Fred Sarazin and I secured the first NSF grant for astroparticle physics at Mines. Organized a team to replace that system and upgraded the first, (Eric Mayotte who was a grad student at the time can tell you more about that experience). About 2012, we decided to expand the reach of the group by joining the JEM-EUSO collaboration. Although the goal of putting a fluorescence telescope to measure cosmic ray airshows from the ISS didn’t pan out, I participated in three balloon experiments to test techniques and instruments needed to measure high energy cosmic rays from the vantage point of space. I served as international deputy PI and project manager for the last two. Anyway, Mines is now on the map in astroparticle physics. It’s been a team effort including many great graduate and undergraduate students, and tremendous support from administrative and shop staff.

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