Default-off inter-qubit interactions in NMR quantum computing in   rotating solids
  A dipolar recoupling technique is introduced as a new approach to quantum gate operation in solid-state NMR under magic angle spinning. The default-off property of inter-qubit interaction provides a simple way to controlled operation without requiring elaborate qubit-decoupling pulses. 
Kazuyuki Takeda, Hiromitsu Tanabe, Masahiro Kitagawa