Events at Physics |
Events on Thursday, July 9th, 2026
- Thesis Defense
- Search for Neutrinos with Energy Greater than 10^17 eV Using All 5 Stations of the Askaryan Radio Array at the South Pole
- Time: 10:00 am - 12:00 pm
- Place: Chamberlin 5310
- Speaker: Abigal Bishop
- Abstract: Ultra-high energy (UHE, 10^17 eV) neutrinos are rare messengers which are valuable for understanding the UHE cosmic ray flux, composition, and origin. When UHE neutrinos interact in dielectric media, they initiate particle cascades that emit optical-wavelength Cherenkov and radio-wavelength Askaryan emission. The highest energy neutrino reported had an energy of ∼ 220 PeV and was detected by the KM3NeT Collaboration via Cherenkov Radiation in the Mediterranean Sea [Aiello et al., 2025]. At higher energies, neutrino interactions are expected to only occur once per year per square kilometer [Navas et al., 2024]. Monitoring ice for Askaryan Radiation is powerful due to long attenuation and scattering lengths for radio waves in ice, allowing a single detector to monitor for rare UHE neutrino interactions over many cubic kilometers. This thesis presents the neutrino search through 10.6 yrs of data taken by the Askaryan Radio Array at the South Pole. Many techniques for background rejection are presented and used along with updated detector simulations. This analysis finds 0 neutrino candidates and therefore establishes an upper limit on the 10^16 eV - 10^21 eV cosmic neutrino flux. This result is also the world-leading upper limit above 4 × 10^19 eV.
- Host: Albrecht Karle
- Thesis Defense
- Tunability of Si/SiGe Quantum Dot Qubit Devices
- Time: 11:00 am - 1:00 pm
- Place: Chamberlin 5280 or
- Speaker: Sanghyeok Park
- Abstract: Gate-defined quantum dots in Si/SiGe heterostructures are a promising platform for spin-based quantum computing because many device parameters can be tuned after fabrication. This tunability gives the platform its flexibility but also makes devices hard to operate reproducibly as they grow. This dissertation uses tunability deliberately in two ways. First, dynamically pulsing a single barrier gate resolves the conflicting tunnel rate requirements of latched readout, enabling single-shot readout of a quantum dot hybrid qubit with a signal-to-noise ratio of 10.2 and a factor of 15 faster reset. Second, gate-biased illumination reshapes the electrostatic environment, shifting a triple quantum dot into a low-voltage regime with a factor of three improvement in voltage uniformity and no measured increase in charge noise. Together these results show how the same gate control that complicates Si/SiGe quantum dots can be used to bring nonuniform devices into a range compatible with compact, scalable control electronics.
- Host: Mark Eriksson