Ground state laser cooling of ions in a Penning trap

Atomic ions held in Penning traps have been used for a wide variety of applications in different areas of physics such as mass spectrometry, precision measurements, plasma physics, atomic physics, antihydrogen production, etc. For applications in quantum optics and quantum information processing, it may be necessary to prepare ions in the ground state of their motion in the trap. This can be achieved with optical sideband cooling, a technique that is used widely in experiments employing RF traps. I will report experiments at Imperial College London where we have for the first time demonstrated optical sideband cooling of an ion in a Penning trap, which presents several complications compared to an RF trap. All ion traps are subject to undesired heating of ground-state cooled ions, but in our system we have measured the lowest heating rate for any ion trap to date, and have demonstrated coherent manipulation of the quantum state of the ion with a long coherence time. I will also describe our most recent results for ground state cooling of two-ion Coulomb crystals in the trap.