This proposal aims to apply ion-trap quantum logic techniques to precision measurements on individual (anti-)protons for fundamental physics tests. In particular, we aim to measure g-factors of single (anti-)protons as a precise test of CPT symmetry. This requires a method to detect single (anti-)proton spin flips. Current efforts based on classical “magnetic bottle” techniques are hurt by the extreme difficulty and slowness of the spin state detection. Discrete and direct state measurement is a prerequisite for inaccuracies below 10-6 and has not been achieved yet.
Towards this end, we will employ a radically different approach and use quantum logic techniques developed by the PI in the NIST ion storage group of D. J. Wineland [Nature 476, 181(2011); Nature 471, 196(2011)]. This will allow us to transfer the (anti-)proton’s spin state to a nearby trapped atomic “logic” ion and subsequently read it out using standard quantum logic detection techniques along the lines of Heinzen and Wineland [PRA 42, 2977; J. Res. NIST 103, 259 (1998)]. The same ideas are also at the root of NIST’s world-record single-ion Al+ frequency standard.
Ultimately, this quantum logic technique will lead to a precise test of CPT symmetry, a fundamental symmetry within the standard model of particle physics, by comparing the proton’s and the antiproton’s g-factor with fast detection and single spin-flip resolution. It thus has the potential to reach inaccuracies below 10-9, exceeding the state-of-the-art for the antiproton g-factor by six orders of magnitude. Such a measurement is urgently needed to complement ongoing tests with electrons and positrons. It is closely intertwined with our desire to understand the observed matter-antimatter imbalance in the universe and to obtain a unified description of matter and interactions. Further, the project will considerably broaden the arsenal of quantum state manipulation techniques in Penning traps and possibly impact high precision mass measurement.
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