Efficient Hadronic Operators in Lattice Gauge Theory
  We study operators to create hadronic states made of light quarks in quenched lattice gauge theory. We construct non-local gauge-invariant operators which provide information about the spatial extent of the ground state and excited states. The efficiency of the operators is shown by looking at the wave function of the first excited state, which has a node as a function of the spatial extent of the operator. This allows one to obtain an uncontaminated ground state for hadrons. 
P. Lacock, A. McKerrell, C. Michael, I. M. Stopher, and P. W.   Stephenson