Optical clock spectroscopy in correlated sub-spaces

Roee Ozeri
Department of Physics of Complex Systems, Weizmann Institute of Science, Rehovot 7610001, Israel

In this talk I will describe several recent experiments in which correlated sub-spaces were used in order to improve the spectroscopy of optical clock transitions in trapped-ion systems. In the first experiment, Quantum Ising interaction was used to result in correlated spin-rotations and lead to Heisenberg-limited sensitivity in the interrogation of the optical clock transition. In a second experiment a correlated sub-space of two Sr+ isotopes was used as an atomic clock with fractional frequency stability and accuracy at the 10^-10 level and which operates at the isotope-shift frequency of the optical clock transition. By comparing this clock to a Cs reference the isotope shift was measured with accuracy below 0.1 Hz. This type of accurate isotope shift measurements can be used to search for new scalar forces in nature. Finally, I will describe a proposal to use an entangled sub-space of two optical clock transitions in two difference atomic species to engineer and optical atomic clock with reduced sensitivity to black-body radiation.