We review experimental progress on optical atomic clocks and frequency transfer, and
consider the prospects of using these technologies for geodetic measurements. Today …

Within the last decade, optical atomic clocks have surpassed the best cesium clocks, which
are used to realize the unit of time and frequency, in terms of accuracy and stability by about …

We provide an overview on terahertz (THz) frequency metrology, starting from the nowadays
available continuous wave THz sources, discussing their main features such as tunability …

Accurate time-delay measurement is at the core of many modern technologies. We present a
temporal-mode demultiplexing scheme that achieves the ultimate quantum precision for the …

The next generation of space-based networks for communications, sensing, and navigation
will contain optical clocks embedded within satellites. To fully realize the capabilities of such …

The ability to distribute the precise time and frequency from an optical clock to remote
platforms could enable future precise navigation and sensing systems. Here, we …

We summarise the discussions at a virtual Community Workshop on Cold Atoms in Space
concerning the status of cold atom technologies, the prospective scientific and societal …

Global Positioning System (GPS) dissemination of frequency standards is ubiquitous at
present, providing the most widespread time and frequency reference for the majority of …

The theory of general relativity was born more than one hundred years ago, and since the
beginning has striking prediction success. The gravitational redshift effect discovered by …

We realize a coherent fiber link for application in very long baseline interferometry (VLBI) for
radio astronomy and geodesy. A 550-km optical fiber connects the Italian National …