Engineering Large Stark Shifts for Control of Individual Clock State   Qubits
  In quantum information science, the external control of qubits must be balanced with the extreme isolation of the qubits from the environment. Atomic qubit systems typically mitigate this balance through the use of gated laser fields that can create superpositions and entanglement between qubits. Here we propose the use of high-order optical Stark shifts from optical fields to manipulate the splitting of atomic qubits that are insensitive to other types of fields. We demonstrate a fourth-order AC Stark shift in a trapped atomic ion system that does not require extra laser power beyond that needed for other control fields. We individually address a chain of tightly-spaced trapped ions and show how these controlled shifts can produce an arbitrary product state of ten ions as well as generate site-specific magnetic field terms in a simulated spin Hamiltonian. 
Aaron C. Lee, Jacob Smith, Philip Richerme, Brian Neyenhuis, Paul W.   Hess, Jiehang Zhang, Christopher Monroe
physics.atom-ph quant-ph