Achieving the Ultimate Quantum Timing Resolution

Accurate time-delay measurement is at the core of many modern technologies. Here, we present a temporal-mode demultiplexing scheme that achieves ultimate quantum precision for simultaneous estimation temporal centroid, time offset, and relative intensities an incoherent mixture ultrashort pulses single-photon level. We experimentally resolve separations ten times smaller than pulse duration, as well imbalanced differing by factor $10^{2}$. This represents improvement more order magnitude over best standard methods based on intensity detection.