Optical interferometry in the presence of large phase diffusion

Phase diffusion represents a crucial obstacle toward the implementation of high-precision interferometric measurements and phase-shift-based communication channels. Here we present a nearly optimal interferometric scheme based on homodyne detection and coherent signals for the detection of a phase shift in the presence of large phase diffusion. In our scheme the ultimate bound to interferometric sensitivity is achieved already for a small number of measurements, of the order of hundreds, without using nonclassical light.