Progress towards an optimized ¹²⁹Xe / ³He Zeeman maser and a test of boost symmetry

Abstract

We report on a search for an annual variation of a daily sidereal modulation of the frequency difference between co-located ¹²⁹Xe and ³He Zeeman masers that sets a stringent limit on boost-dependent Lorentz and CPT violation involving the neutron, consistent with no effect at the level of 150 nHz. In the framework of the general Standard-Model Extension, our result provides the first clean test for the fermion sector of the symmetry of spacetime under boost transformations at a level of 10-27 GeV [1]. We also report progress on the optimization and operation of the Harvard-Smithsonian ¹²⁹Xe/³He dual noble gas maser. The ¹²⁹Xe/³He maser is the first device to sustain simultaneous active maser oscillations on distinct transitions in two intermingled atomic species, and it allows sensitive differential measurement of the ¹²⁹Xe and ³He nuclear spin-1/2 Zeeman transition frequencies [2, 3, 4]. The optimized ¹²⁹Xe /³He maser will be used for highly sensitive tests of Lorentz and CPT symmetry.