Mode invisibility as a quantum non-demolition measurement of coherent   light
  We exploit geometric properties of quantum states of light in optical cavities to carry out quantum non-demolition measurements. We generalize the 'mode invisibility' method to obtain information about the Wigner function of a squeezed coherent state in a non-destructive way. We also simplify the application of this non-demolition technique to measure single-photon and few-photon states. 
Marvellous Onuma-Kalu, Robert B. Mann and Eduardo Martin-Martinez
quant-ph