Photons and qubits in a continuous-variable aspect

I review optical homodyne tomography as a method for precise characterization of photons, qubits, and elementary optical information processors. While being more challenging technically, this continuous-variable method provides much more accurate information about optical ensembles than traditional photon-counting based tech-niques. The application of continuous-variable tomography to discrete optical states creates a bridge between these two formerly distinct areas of quantum optics.