Quantum-Limited Detection and Special Relativity: Promising New Tools for Greatly Improved Electron Magnetic Moment Measurements
Benedict Sukra
Ph.D. Student
Center for Fundamental Physics
Department of Physics & Astronomy
Northwestern University
The most precise test of the Standard Model (SM) is the comparison of the measured and predicted values of the electron’s magnetic moment [1–4]. This comparison, at the sub-parts-per-trillion level, tightly constrains new theoretical models, and any observed discrepancy would point to physics beyond the SM.
In this talk, I will discuss two promising approaches that together could yield a tenfold improvement in future measurements. First, we employ a quantum-limited SQUID amplifier to read out the state of our single-electron qubit system, drastically reducing thermal noise and enabling more precise detection. Second, with this enhanced sensitivity, we harness the relativistic mass shift from individual spin flips and cyclotron jumps to realize quantum non-demolition (QND) detection. This strategy reduces the trapped electron’s temperature by a factor of 20—narrowing measured resonance linewidths and significantly mitigating systematic uncertainties.
These innovations, along with improvements in measurements of the fine-structure constant (leading to a more precise SM prediction), are projected to advance this test of the SM by at least a factor of 10.
*Supported by the NSF, with detector development supported by the Templeton Foundation and trap cavity development support by the DOE SQMS Center.
1. X. Fan, T. G. Myers, B. A. D. Sukra, and G. Gabrielse, Phys. Rev. Lett. 130, 071801 (2023)
2. R. H. Parker, C. Yu, W. Zhong, B. Estey, and H. Müller, Science 360 (2018) 191
3. Léo Morel, Zhibin Yao, Pierre Cladé & Saïda Guellati-Khélifa, Nature Vol. 588, pg 61–65 (2020)
4. T. Aoyama, T. Kinoshita, M. Nio, Atoms 2019, 7, 28.
Hosted by Prof. Brodeur