Quantum-Limited Detection and Special Relativity: Promising New Tools for Greatly Improved Electron Magnetic Moment Measurements

The most precise test of the Standard Model (SM) is the comparison of its prediction of the electron’s magnetic moment with its measured value [1-4]. This comparison, at the sub-parts per trillion level, is a powerful tool in our search for physics beyond the SM as any deviations between measurement and prediction would point to new physics. Additionally, it provides a strong constraint on new physics as any new theoretical model must agree with this measurement.

In this talk I will discuss two promising approaches that together promise a factor of 10 improvement in future measurements. The first is employing a quantum-limited detector (SQUID amplifier) to perform state readout of our single-electron qubit system. The second is to use the relativistic mass shift due to spin-flips and cyclotron jumps for “quantum non-demolition” (QND) detection of our qubit state. This will allow us to reduce the electron’s temperature by a factor of 20 leading to reductions in resonance linewidths by this factor and a large reduction in current systematic errors.

This elegant new approach along with expected improvements in the SM prediction, arising from improved measurements in the fine structure constant, would improve the most precise test of the SM by a factor of 100.

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.