Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Measuring absolute frequencies beyond the GPS limit via long-haul
  optical frequency dissemination   Global Positioning System (GPS) dissemination of frequency standards is
ubiquitous at present, providing the most widespread time and frequency
reference for the majority of industrial and research applications worldwide.
On the other hand, the ultimate limits of the GPS presently curb further
advances in high-precision, scientific and industrial applications relying on
this dissemination scheme. Here, we demonstrate that these limits can be
reliably overcome even in laboratories without a local atomic clock by
replacing the GPS with a 642-km-long optical fiber link to a remote primary
caesium frequency standard. Through this configuration we stably address the
$^1$S$_0$---$^3$P$_0$ clock transition in an ultracold gas of $^{173}$Yb, with
a precision that exceeds the possibilities of a GPS-based measurement,
dismissing the need for a local clock infrastructure to perform high-precision
tasks beyond GPS limit. We also report an improvement of two orders of
magnitude in the accuracy on the transition frequency reported in literature.

29
The categories of this paper are: funct-an
21
The categories of this paper are: adap-org
12
The categories of this paper are: nucl-th
20
The categories of this paper are: acc-phys
36
The categories of this paper are: cmp-lg
2
The categories of this paper are: math
23
The categories of this paper are: solv-int
14
The categories of this paper are: math-ph
24
The categories of this paper are: dg-ga
31
The categories of this paper are: ao-sci
7
The categories of this paper are: hep-th
16
The categories of this paper are: stat
22
The categories of this paper are: chao-dyn
17
The categories of this paper are: q-fin
9
The categories of this paper are: nlin
19
The categories of this paper are: eess