The Use of Quantum Dots as Highly Sensitive Switchs Based on   Singlet-Triplet Transition and Symmetry Constraint
  Based on symmetry constraint that leads to the appearance of nodes in the wave functions of 3-electron systems at regular triangle configurations, it was found that, if the parameters of confinement are skillfully given and if a magnetic field is tuned around the critical point of the singlet-triplet transition, a 2-electron quantum dot can be used as a highly sensitive switch for single-electron transport. 
Y.M.Liu, G.M.Huang, C.G.Bao