Improved bounds on Lorentz violation from composite-pulse Ramsey spectroscopy in a trapped ion

Abstract

Gravity is not understood at a quantum mechanical level. In an attempt to formulate a single quantum-consistent theory of the four known fundamental forces, it is suggested that spontaneous breaking of Lorentz symmetry might occur at the Planck scale 1,2 . In the low-energy limit, such a Lorentz violation would give rise to small shifts of energy levels with non-spherical atomic orbitals 3 . These could be observed with precision spectroscopy of atoms in a Michelson-Morley type experiment using Earth's rotation [4][5][6] . In this work we perform such an experiment in the long-lived electronic 2 F 7/2 manifold of the Yb + ion. We exploit the high intrinsic susceptibility of this state to Lorentz violation 7 and apply an elaborate radio-frequency spin-echoed Ramsey sequence 8 to investigate the isotropy of space-time with a single trapped ion. A robust composite pulse sequence allows us to extend the coherence time to more than 1 s and accurately compare the orthogonally oriented sublevels of the Zeeman manifold. With a three times higher sensitivity to Lorentz violation compared to the best test to date 6 , we improve the constraints on all the measured Lorentz symmetry breaking coefficients and set their bounds at the 10 −21 level. These results represent the most stringent test of this type of Lorentz violation in the electron-photon sector. The method is readily extendable to multiple ions in Coulomb crystals, enabling improved tests of Lorentz symmetry in the near future.

Impact of Lorentz violation on anomalous magnetic moments of charged leptons

“…Various anisotropic combinations of c have already been severely constrained by laboratory experiments, which is, e.g. backed up by the very recent analysis [117] in the electron sector providing bounds at the 10 −21 level. Astrophysics gives rise to few competitive limits on the isotropic part of c in electrons [96], whereas laboratory experiments, in general, are not that sensitive to isotropic modifications.…”