Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Quantum repeaters in space   Long-distance entanglement is a very precious resource, but its distribution
is very difficult due to the exponential losses of light in optical fibres. A
possible solution consists in the use of quantum repeaters, based on
entanglement swapping or quantum error correction. Alternatively,
satellite-based free-space optical links can be exploited, achieving better
loss-distance scaling. We propose to combine these two ingredients, quantum
repeaters and satellite-based links, into a scheme that allows to achieve
entanglement distribution over global distances with a small number of
intermediate untrusted nodes. The entanglement sources, placed on satellites,
send quantum states encoded in photons towards orbiting quantum repeater
stations, where entanglement swapping is performed. The performance of this
repeater chain is assessed in terms of the secret key rate achievable by the
BB-84 cryptographic protocol. We perform a comparison with other repeater chain
architectures and show that our scheme is superior in almost every situation,
achieving higher key rates, reliability and flexibility. Finally, we analyse
the feasibility of the implementation in the mid-term future and discuss
exemplary orbital configurations. The integration of satellite-based links with
ground repeater networks can be envisaged to represent the backbone of the
future Quantum Internet.

6
The categories of this paper are: astro-ph
20
The categories of this paper are: acc-phys
19
The categories of this paper are: eess
28
The categories of this paper are: alg-geom
14
The categories of this paper are: math-ph
21
The categories of this paper are: adap-org
11
The categories of this paper are: hep-lat
35
The categories of this paper are: mtrl-th
8
The categories of this paper are: hep-ex
17
The categories of this paper are: q-fin
29
The categories of this paper are: funct-an
34
The categories of this paper are: chem-ph
30
The categories of this paper are: q-alg
1
The categories of this paper are: cs
22
The categories of this paper are: chao-dyn
33
The categories of this paper are: plasm-ph