We review the most recent progress in ultralow-noise mode-locked fiber lasers and fiber-
based frequency-comb sources. With the rapid progress in theory, measurement, and …

Optical clocks show unprecedented accuracy, surpassing that of previously available clock
systems by more than one order of magnitude. Precise intercomparisons will enable a …

To compare the increasing number of optical frequency standards, highly stable optical
signals have to be transferred over continental distances. We demonstrate optical-frequency …

The transfer of high-quality time–frequency signals between remote locations underpins
many applications, including precision navigation and timing, clock-based geodesy, long …

Some background as well as recent progress in the development of femtosecond lasers are
discussed together with a brief outline of a few representative emergent applications in …

To significantly improve the frequency references used in radio-astronomy and the precision
measurements in atomic physics, we provide frequency dissemination through a 642-km …

We describe a VLBI experiment in which, for the first time, the clock reference is delivered
from a National Metrology Institute to a radio telescope using a coherent fibre link 550 km …

The microwave caesium (Cs) atomic clock has formed an enduring basis for the second in
the International System of Units (SI) over the last few decades. The advent of laser cooling …

Abstract The Square Kilometre Array (SKA) project is an international effort to build the
world's largest radio telescope, with a one-square-kilometre collecting area. In addition to its …

Based on the second-order quantum interference between frequency entangled photons
that are generated by parametric down conversion, a quantum strategic algorithm for …