Quantum optical technology at the single-photon level and beyond

Latest progress in quantum optical engineering allows us to synthesize increasingly complex quantum states of light. At the same time, the progress in optical homodyne tomography, particularly in application to "discrete-variable" optical states that are useful in quantum information technology, leads to fundamental improvement in the accuracy of quantum-state characterization. These developments constitute a qualitative advance in quantum optical technology because they open up a vast new region of the Hilbert space that was previously not accessible for experimental investigation. The gap between "discrete-" and "continuous-variable" quantum optics is closing.