Quantum Logic Spectroscopy of an Electron and Positron
Testing the Standard Model with Quantum Logics
A Penning trap is a powerful tool for measuring the properties of elementary particles. An electron or a positron can be stored in a cryogenic environment and cooled to its motional ground state. Based on the past measurement of the electron's magnetic moment at the 13-digit precision, we proposed a new method of improving the precision by another order of magnitude using quantum logic spectroscopy.
The current goals are
Electron and positron's g-factor measurement at 14 digits of precision.
The electron's g-factor is the most precise prediction of the Standard Model. The value has been measured at 13-digit precision as
g/2=1.001 159 652 180 59 (13)
The measurement gives the most precise test of the Standard Model's calculation, and precise determination of the fine structure constant.
(a) Measured g/2 in 2022 vs the previous g/2 measurement and Standard Model predictions using the fine-structure constant measured by Cesium and Rubidium. (b) fine-structure constant determination using the measured g/2 and the Standard Model calculation.
We are now working on improving the measurement to 14-digit precision using quantum logic spectroscopy. An electron or positron in a spectroscopy trap is coupled to another electron or positron in a readout trap. A wire between them creates coupling, allowing quantum SWAP gate operation between them. By separating the function of the two traps, we anticipate 20 times improved magnetic field homogeneity, 30 times higher detection efficiency, and 7 times better control of systematic errors.
Importantly, an improved measurement will also test the muon g-2 discrepancy independently. If the observed muon g-2's discrepancy is real, one can scale it to the electron's g-2 by the square of the mass ratio (m_e/m_μ)^2. The expected precision to test this is only a factor of 2 away from our 2023 measurement. Improved measurement at 14-digit precision will test the discrepancy at 5 5-sigma confidence level.
