Experimental characterization of bosonic photon creation and   annihilation operators
  The photon creation and annihilation operators are cornerstones of the quantum description of the electromagnetic field. They signify the isomorphism of the optical Hilbert space to that of the harmonic oscillator and the bosonic nature of photons. We perform complete experimental characterization (quantum process tomography) of these operators. By measuring their effect on coherent states, we obtain their process tensor in the Fock basis, which explicitly shows the "raising" and "lowering" properties of these operators with respect to photon number states. This is the first experimental demonstration of complete tomography of non-deterministic quantum processes. 
R. Kumar, E. Barrios, C. Kupchak, A. I. Lvovsky
quant-ph physics.optics