Quantum gates using electronic and nuclear spins of Yb$^{+}$ in a   magnetic field gradient
  An efficient scheme is proposed to carry out gate operations on an array of trapped Yb$^+$ ions, based on a previous proposal using both electronic and nuclear degrees of freedom in a magnetic field gradient. For this purpose we consider the Paschen-Back regime (strong magnetic field) and employ a high-field approximation in this treatment. We show the possibility to suppress the unwanted coupling between the electron spins by appropriately swapping states between electronic and nuclear spins. The feasibility of generating the required high magnetic field is discussed. 
Kunling Wang, Michael Johanning, Mang Feng, Florian Mintert, Christof   Wunderlich
quant-ph