Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Experimental quantum key distribution beyond the repeaterless secret key
  capacity   Quantum communications promise to revolutionise the way information is
exchanged and protected. Unlike their classical counterpart, they are based on
dim optical pulses that cannot be amplified by conventional optical repeaters.
Consequently they are heavily impaired by propagation channel losses, which
confine their transmission rate and range below a theoretical limit known as
repeaterless secret key capacity. Overcoming this limit with today's technology
was believed to be impossible until the recent proposal of a scheme that uses
phase-coherent optical signals and an auxiliary measuring station to distribute
quantum information. Here we experimentally demonstrate such a scheme for the
first time and over significant channel losses, in excess of 90 dB. In the high
loss regime, the resulting secure key rate exceeds the repeaterless secret key
capacity, a result never achieved before. This represents a major step in
promoting quantum communications as a dependable resource in today's world.

30
The categories of this paper are: q-alg
16
The categories of this paper are: stat
5
The categories of this paper are: gr-qc
32
The categories of this paper are: atom-ph
27
The categories of this paper are: comp-gas
21
The categories of this paper are: adap-org
17
The categories of this paper are: q-fin
12
The categories of this paper are: nucl-th
26
The categories of this paper are: bayes-an
29
The categories of this paper are: funct-an
6
The categories of this paper are: astro-ph
34
The categories of this paper are: chem-ph
36
The categories of this paper are: cmp-lg
23
The categories of this paper are: solv-int
11
The categories of this paper are: hep-lat
0
The categories of this paper are: hep-ph