## Position in Innsbruck

The Innsbruck team has an open theory ESR (PhD) position.

Optical atomic clocks need stable oscillators as flywheels. In principle, superradiant lasers operating directly on the atomic clock transition are a viable option, providing an intrinsically precise and accurate frequency reference. Implementation requires a gain from a large ensemble of ultra-cold inverted atoms trapped in magic wavelength optical fields within the mode volume of a high Q resonator. As a consequence the high density creates unwanted direct dipole-dipole interactions and collective decay generating frequency noise and mutual interaction forces heating up the atomic motion. The dynamical consequences and limitations induced by this coupling will be numerically studied by the ESR starting from simple few particle systems to work out the basic physical effects. These will be be extended to include atomic motion, collisions and loss. In particular, the pumping needed for a stationary operation is treated unsatisfactorily only in most current models and should be modelled in a more realistic way inspired by maser models. In a further step, generalization to larger particle numbers beyond a mean field treatment needs to be tackled, e.g. via a systematic cumulant expansion of atom field correlation functions. Everything has to be tested by extensive numerical simulations of coupled particle and field equations. Possible methods range from direct numerical integration of the master equation to stochastic wave function simulations to the benchmark the symmetry based cluster expansions of the coupled atom field dynamics. Here efficient codes developed in iqClock can be adapted.

For more information please contact Helmut Ritsch.

To apply for a position send your CV.

**ESR12 - Optical forces and dipole-dipole interaction in a superradiant optical clock**Optical atomic clocks need stable oscillators as flywheels. In principle, superradiant lasers operating directly on the atomic clock transition are a viable option, providing an intrinsically precise and accurate frequency reference. Implementation requires a gain from a large ensemble of ultra-cold inverted atoms trapped in magic wavelength optical fields within the mode volume of a high Q resonator. As a consequence the high density creates unwanted direct dipole-dipole interactions and collective decay generating frequency noise and mutual interaction forces heating up the atomic motion. The dynamical consequences and limitations induced by this coupling will be numerically studied by the ESR starting from simple few particle systems to work out the basic physical effects. These will be be extended to include atomic motion, collisions and loss. In particular, the pumping needed for a stationary operation is treated unsatisfactorily only in most current models and should be modelled in a more realistic way inspired by maser models. In a further step, generalization to larger particle numbers beyond a mean field treatment needs to be tackled, e.g. via a systematic cumulant expansion of atom field correlation functions. Everything has to be tested by extensive numerical simulations of coupled particle and field equations. Possible methods range from direct numerical integration of the master equation to stochastic wave function simulations to the benchmark the symmetry based cluster expansions of the coupled atom field dynamics. Here efficient codes developed in iqClock can be adapted.

For more information please contact Helmut Ritsch.

To apply for a position send your CV.