Variance-based uncertainty relations for incompatible observables
  We formulate uncertainty relations for arbitrary finite number of incompatible observables. Based on the sum of variances of the observables, both Heisenberg-type and Schr\"{o}dinger-type uncertainty relations are provided. These new lower bounds are stronger in most of the cases than the ones derived from some existing inequalities. Detailed examples are presented. 
Bin Chen, Ning-Ping Cao, Shao-Ming Fei, Gui-Lu Long
quant-ph