Events at Physics |
Events During the Week of January 29th through February 5th, 2023
Monday, January 30th, 2023
- Atomic Physics Seminar
- Where is All the Antimatter? Electron EDM Search in Cold Molecules Edges Closer
- Time: 11:00 am - 12:00 pm
- Place: 5310 Chamberlin Hall
- Speaker: Xing Wu, Harvard University
- Abstract: The Standard Model of particle physics accurately describes all fundamental particles discovered so far. However, it is unable to address two great mysteries in physics, the nature of dark matter and why matter dominates over antimatter throughout the Universe. Novel theories beyond the Standard Model, such as models that incorporate supersymmetry, may explain these phenomena. These models predict very massive particles whose interactions violate time-reversal (T) symmetry and would give rise to an electric dipole moment (EDM) along the electron’s spin. Thus, searching for EDM provides a powerful probe to these new physics and sheds light on the mystery of the matter-antimatter asymmetry of the Universe.
Here, I share with you the exciting journey of the ACME electron EDM search that has set the recent best limit on the value of electron EDM, measured by spin precession in a superposition of quantum states in cold molecules. This result severely constrains T-violating new physics in 330 TeV energy range, exceeding what can be reached at the Large Hadron Collider. New upgrades employing various quantum control and AMO techniques are now underway, projecting over an order of magnitude sensitivity enhancement ffor the next EDM search.
- Host: Thad Walker
- Plasma Physics (Physics/ECE/NE 922) Seminar
- CANCELLATION: No seminar for Monday, January 30, 2023
- Time: 12:00 pm - 6:00 pm
- Place: 2241 Chamberlin Hall
- Host: Plasma Physics/ECE/NE 922 seminar
Tuesday, January 31st, 2023
- R. G. Herb Condensed Matter Seminar
- Locality, universality, and quantum dynamics with measurements
- Time: 10:00 am - 6:00 pm
- Place: 5310 Chamberlin
- Speaker: Aaron Friedman, UC Boulder
- Abstract: I will present a recently developed formalism for quantum measurements that is both technically powerful and conceptually transparent. This framework is the basis for new results based on condensed matter principles like locality and universality that were not previously thought possible—including extending the Lieb-Robinson Theorem to dynamics with measurements and proving deep connections between measurement-based quantum computation and topological order. In contrast to the conventional wisdom that measurements destroy locality, we find a maximum enhancement to the speed of quantum information in measurement-assisted protocols, establishing a precise notion of locality. I’ll discuss the formal resolution to the EPR paradox, constraints on quantum teleportation, error correction, routing, and the preparation of useful resource states (e.g., Bell, GHZ, Dicke, and squeezed states). I’ll present optimal quantum protocols that achieve these tasks, reveal new resource tradeoffs, and discuss important implications for measurement-based quantum computing and its fundamental connection to symmetry-protected topological order. Finally, I'll comment on other applications relevant to condensed matter and future applications of this work.
- Host: Victor Brar
- Network in Neutrinos, Nuclear Astrophysics, and Symmetries (N3AS) Seminar
- High-Energy Multimesssenger Emission from Supermassive Black Holes
- Time: 2:00 pm
- Place: Join Zoom Meeting Meeting ID: 912 3071 4547
- Speaker: Kohta Murase, Penn State
- Abstract: Supermassive black holes power disks, coronae, jets and winds, and a significant fraction of energy released by the black holes may be carried by cosmic rays and associated high-energy non-thermal radiation. Recently, the IceCube Collaboration reported associations of high-energy neutrinos with active galactic nuclei, including a nearby Seyfert galaxy, NGC 1068. We review the implications of the multimessenger data for theoretical models and discuss their challenges.
- Host: Baha Balantekin
Wednesday, February 1st, 2023
- Academic Calendar
- Deadline to drop a course or withdraw from the university without having the course(s) appear on the transcript
- Abstract: *Note: actual end time may vary.* CONTACT: 262-3811, registrar@em.wisc.edu URL:
- Atomic Physics Seminar
- Superradiance in ordered atomic arrays
- Time: 11:00 am - 12:00 pm
- Place: 5310 Chamberlin Hall
- Speaker: Stuart Masson , Columbia University
- Abstract: Collective phenomenona are found in every branch of science; the behavior of the whole differs strongly from the behavior of the individual elements. In quantum optics, a hallmark example is Dicke superradiance. Here, a fully inverted ensemble of atoms emits a short and bright light pulse, known as the superradiant burst, that initially grows in intensity. This is in stark contrast to independent atoms which decay exponentially, emitting a pulse that monotonically decreases in time. Experiments in dense disordered systems have observed the superradiant burst, but there, inhomogeneous broadening plays a large role, making the systems hard to model or control. In contrast, ordered arrays have much lower inhomogeneity - atoms in the bulk all see the same set of neighbors - making them an ideal platform to study dissipative many-body physics. Here, we show the conditions under which such systems produce a superradiant burst. We go beyond two-level approximations, and demonstrate that long-wavelength transitions from ytterbium and strontium atoms can be used to observe such physics. Our work represents an important step in harnessing such systems to build quantum optical sources and as dissipative generators of entanglement.
- Host: Thad Walker
Thursday, February 2nd, 2023
- R. G. Herb Condensed Matter Seminar
- Emergence of Quantum Order
- Time: 10:00 am - 6:00 pm
- Place: 5310 Chamberlin
- Speaker: Elio Konig , Max Planck (Stuttgart)
- Abstract: The patterns of self-organization in complex quantum systems are traditionally understood using the concept of spontaneous symmetry breaking. In contrast, quantum order in the absence of symmetry breaking, in particular highly entangled topologically ordered states, describe fundamentally distinct phases of matter which are of great interest both in present-day condensed matter research and in quantum information science. In this talk, I will spend some time reviewing the concepts of topological and non-symmetry broken quantum order. I will then focus on the interplay of such exotic states with gapless fermions, i.e., metals. I will discuss their importance as solid-state realizations of lattice gauge theories, mechanisms in which a Fermi sea stabilizes miniature variants of topological order, and experimental setups in which metallic contacts are used to probe quantum order. I will conclude with an outlook summarizing the multiple synergies of quantum information theory and quantum materials science.
- Host: Victor Brar
- Astronomy Colloquium
- The discovery and properties of binary-stripped helium stars
- Time: 3:30 pm - 4:30 pm
- Place: 4421 Sterling Hall
- Speaker: Ylva Götberg, Carnegie Observatories
- Abstract: Massive stars stripped of their H-rich envelopes through mass transfer or common envelope ejection are thought to be the main progenitors of H-poor supernovae, to emit large amounts of hard ionizing radiation, and to constitute two necessary steps in the binary evolution pathways towards compact objects merging in gravitational wave events. Despite their importance, these stripped helium stars have remained elusive. With new UV photometry combined with optical magnitudes, and follow-up optical spectroscopy, we identified a first sample of dozens of such stripped star systems in the Magellanic Clouds. We obtain estimates for their stellar parameters by fitting their optical spectra to a newly computed grid of helium star atmosphere models. Aligned with theoretical expectations, we find that stripped stars are hot (Teff~50-100 kK), compact (log g ~ 5), He-rich (Y_surf ~0.6-1), and H-poor (X_surf ~0-0.4). Furthermore, by matching the spectroscopic fits with the photometrical data, we find small radii (~1 Rsun), a range of luminosities (L ~ 1,000-100,000 Lsun), and masses that are sufficient to lead to core-collapse (~2-8 Msun). There are strong indications that the stellar winds are surprisingly weak, suggesting that binary-stripped helium stars are the main responsible for both IIb and Ib supernovae. Apart from providing an observational anchor for both binary evolution models and simulations of common envelope ejection, this sample of stars proves that the full mass range of helium stars exists, forming a bridge between subdwarfs and Wolf-Rayet stars.
- Host: Ke Zhang
- Astronomy Colloquium
- The Discovery and Properties of Binary-Stripped Helium Stars
- Time: 3:30 pm - 4:30 pm
- Place: 4421 Sterling Hall
- Speaker: Dr. Ylva Götberg , Carnegie Observatories
- Abstract: Massive stars stripped of their H-rich envelopes through mass transfer or common envelope ejection are thought to be the main progenitors of H-poor supernovae, to emit large amounts of hard ionizing radiation, and constitute two necessary steps in the binary evolution pathways towards compact objects merging in gravitational wave events. Despite their importance, these stripped helium stars have remained elusive. With new UV photometry combined with optical magnitudes, and follow-up optical spectroscopy, we identified the first sample of dozens of such stripped star systems in the Magellanic Clouds. We obtain estimates for their stellar parameters by fitting their optical spectra to a newly computed grid of helium star atmosphere models. Aligned with theoretical expectations, we find that stripped stars are hot (Teff~50-100 kK), compact (log g ~ 5), He-rich (Y_surf ~0.6-1), and H-poor (X_surf ~0-0.4). Furthermore, by matching the spectroscopic fits with the photometrical data, we find small radii (~1 Rsun), a range of luminosities (L ~ 1,000-100,000 Lsun), and masses that are sufficient to lead to core-collapse (~2-8 Msun). There are strong indications that the stellar winds are surprisingly weak, suggesting that binary-stripped helium stars are the main ones responsible for both IIb and Ib supernovae. Apart from providing an observational anchor for both binary evolution models and simulations of common envelope ejection, this sample of stars proves that the full mass range of helium stars exists, forming a bridge between subdwarfs and Wolf-Rayet stars.
Friday, February 3rd, 2023
- Academic Calendar
- Deadline for students to add, swap, or change sections in a Spring term course
- Abstract: *Note: actual end time may vary.* CONTACT: 262-3811, registrar@em.wisc.edu URL:
- Academic Calendar
- Deadline for students to begin initial Spring enrollment
- Abstract: *Note: actual end time may vary.* CONTACT: 262-3811, registrar@em.wisc.edu URL:
- Academic Calendar
- Deadline for students to drop a Spring term course and receive 100% tuition adjustment
- Abstract: *Note: actual end time may vary.* CONTACT: 262-3811, registrar@em.wisc.edu URL:
- NPAC (Nuclear/Particle/Astro/Cosmo) Forum
- Exploiting stellar explosion induced by the QCD phase transition in large-scale neutrino detectors
- Time: 2:00 pm - 3:00 pm
- Place: CH4274/https://uwmadison.zoom.us/j/94714568988?pwd=TnRuZFNQaFErZDZ6V29DL0VpSC9rUT09
- Speaker: Anna Suliga, UC Berkeley/UW Madison
- Abstract: Core-collapse supernovae are one of the most complex phenomena in the universe. Not only are they one of the sites of the production of the heavy elements which enable the existence of life, but their cores are also one of the densest environments we can indirectly probe. At such densities, the matter may no longer consist only of hadronic degrees of freedom but undergo a phase transition to quark matter. In this talk, I will discuss the implications of such a transition on the neutrino emission from core-collapse supernovae and how the detection of such a signal on Earth can be used to point to the location of the supernova and set stringent limits on the absolute active neutrino mass.
- Host: A. Baha Balantekin
- Physics Department Colloquium
- Multi-messenger scanning probe microscopy for the investigation of electronic properties of materials.
- Time: 3:30 pm - 4:30 pm
- Place: 2241 Chamberlin Hall
- Speaker: Victor Brar, UW Madison
- Abstract: Scanning probe microscopy is an imaging technique whereby a sharp tip is moved across a surface while locally measuring some material property with a resolution that can be sub-Angstrom. A wide range of material properties can be studied in this way, including surface conductance (scanning tunneling microscopy), physical structure (atomic force microscopy), and surface potential (Kelvin probe force microscopy). By combining these measurement techniques, a complete understanding of a material's properties can be developed that relates electron motion to underlying atomic structure. In this talk I will show how multiple scanning probe measurements can be performed on graphene to reveal how electrons scatter off and move around in-plane potential barriers formed by charged defects. By comparing measurements of the spatially varying surface potential with measurements of the electron wavefunction, the electron dynamics can be modeled precisely, and described using a single-particle wavefunction. As the electron temperature is increased, however, these measurements reveal a new hydrodynamic phase of the electron fluid emerges with a viscosity comparable to diesel fuel. Our scanned probe measurements show that this new phase exhibits a conductivity that is greater than ballistic conductance, and that the motion of electrons around barriers resembles that of water moving around pebbles in a stream.