Search for optimum labeling schemes in qubit systems for Quantum   Information processing by NMR
  Optimal labeling schemes lead to efficient experimental protocols for quantum information processing by nuclear magnetic resonance (NMR). A systematic approach of finding optimal labeling schemes for a given computation is described here. The scheme is described for both quadrupolar systems and spin-1/2 systems. Finally, one of the optimal labeling scheme has been used to experimentally implement a quantum full-adder in a 4-qubit system by NMR, using the technique of transition selective pulses. 
Ranabir Das, Sukhendu Chakraborty, K. Rukmani and Anil Kumar