  Interference of light fields plays an important role in various
high-precision measurement schemes. It has been shown that super resolving
phase measurements beyond the standard coherent state limit can be obtained
either by using maximally entangled multi-particle states of light or using
complex detection approaches. Here we show that super resolving phase
measurements at the shot noise limit can be achieved without resorting to
non-classical optical states or to low-efficiency detection processes. Using
robust coherent states of light, high-efficiency homodyne detection and a
deterministic binarization processing technique, we show a narrowing of the
interference fringes that scales with 1/Sqrt{N} where N is the mean number of
photons of the coherent state. Experimentally we demonstrate a 12-fold
narrowing at the shot noise limit.

Quantum Physics