Quantum Control and Entanglement
of Electrons and Positrons
Testing the Standard Model with Quantum-Logic
Please visit https://fanresearchgroup.hsites.harvard.edu/
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Quantum Control and Entanglement
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 goal involves
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.
x300 improved determination of the positron's g-factor and
x1000 improved determination of the positron's mass
Positrons have an attractive feature because of their positive charge. This positive charge allows it to become a comagnetometer with protons, as well as other ions such as Be+ for sympathetic cooling.
Currently, we are developing a trap that can rapidly switch an electron and a positron to achieve this goal. An improved measurement of the electron and positron's g-factor and mass ratio will provide:
The most precise test of the Standard Model of Particle Physics
CPT symmetry violation, Lorentz Symmetry violation, and the SM extension parameters
antigravity effect on leptons at 1% level
Most precise limit on the fifth force between neutrons and electrons
Dark Photon limits at MeV scale
All our developed methods are applicable to electrons and positrons equally. Through exploring physics beyond the Standard Model, we develop innovative methods for future Penning traps.
The electron Penning trap used in the 2023 g-factor measurement.
Second-generation electron and positron Penning trap
Positron trap system for the lepton CPT symmetry test
"The standard" titanium vacuum chamber
Supported by
- U.S. National Science Foundation
- U.S. Department of Energy, SQMS
- John Templeton Foundation
- Masason Foundation (公益財団法人 孫正義育英財団)
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