Spin clocks: Probing fundamental symmetries in nature: Spin clocks: Probing fundamental symmetries in nature

The detection of the free precession of co-located He-3/Xe-129 nuclear spins (clock comparison) is used as ultra-sensitive probe for non-magnetic spin interactions, since the magnetic dipole interaction (Zeeman-term) drops out in the weighted frequency difference, i.e., Delta omega = omega(He)-gamma(He)/gamma(Xe)omega(Xe) of the respective Larmor frequencies. Recent results are reported on searches for (i) short-range P- and T-violating interactions between nucleons, and (ii) Lorentz violating signatures by monitoring the Larmor frequencies as the laboratory reference frame rotates with respect to distant stars (sidereal modulation). Finally, a new experimental initiative to search for an electric dipole moment of Xe-129 (CP-violation) is discussed, which strongly benefits from the long spin-coherence times obtained, reaching T*(2,He) > 100 h and T*(2,Xe) > 8 h in case of He-3 and Xe-129, respectively.