In modern physics we are faced with the unsatisfactory situation that the Standard Model (SM), which condenses our current state of
knowledge in the form of quantum field theories, despite its spectacular success in the prediction of laboratory results, fails in
explaining even the most basic properties of our Universe, such as the disparity of matter and antimatter and the possible existence
of dark matter. In the quest to search for answers to these questions, low energy, high precision experiments in ion traps have taken a
pivotal role by allowing precise tests of the charge, parity and time (CPT) reversal symmetry.
In the LSYM project we develop a next-generation, deep-cryogenic Penning-trap setup that will enable us to directly compare the magnetic moments of electron and positron at 14 digits precision. To this end, we simultaneously trap a single positron and an electron in the same trap and directly compare their spin precession frequencies. To enable the co-trapping of the oppositely charged particle and antiparticle, we bind the electron in a hydrogenlike 4He+ ion. As a result of the binding, the spins of both particles show a slow beat, which can be accurately measured. Any deviation of this beat frequency from the prediction by quantum electrodynamics (QED) would indicate CPT violation. This way, LSYM will enable a uniquely sensitive comparison of particle and antiparticle charge, mass and g-factors and thus yield a stringent CPT test in the lepton sector.
To this end, we are developing a novel, superconducting Penning trap apparatus, which can be cooled to millikelvin temperatures, largely eliminating black-body radiation. In LSYM we can non-destructively determine the spin-state of the bound electron and the positron individually via the continuous Stern-Gerlach effect. A dual-Ramsey sequence on the co-crystallised particles then enables the coherent “quantum” measurement of the difference of the spin precession frequencies.
Furthermore, with this toolbox at hand, we might get access to a new class of intriguing measurements, such as an order of magnitude
improved determination of the electron atomic mass.
