Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Atom chip based generation of entanglement for quantum metrology   Atom chips provide a versatile `quantum laboratory on a microchip' for
experiments with ultracold atomic gases. They have been used in experiments on
diverse topics such as low-dimensional quantum gases, cavity quantum
electrodynamics, atom-surface interactions, and chip-based atomic clocks and
interferometers. A severe limitation of atom chips, however, is that techniques
to control atomic interactions and to generate entanglement have not been
experimentally available so far. Such techniques enable chip-based studies of
entangled many-body systems and are a key prerequisite for atom chip
applications in quantum simulations, quantum information processing, and
quantum metrology. Here we report experiments where we generate multi-particle
entanglement on an atom chip by controlling elastic collisional interactions
with a state-dependent potential. We employ this technique to generate
spin-squeezed states of a two-component Bose-Einstein condensate and show that
they are useful for quantum metrology. The observed 3.7 dB reduction in spin
noise combined with the spin coherence imply four-partite entanglement between
the condensate atoms and could be used to improve an interferometric
measurement by 2.5 dB over the standard quantum limit. Our data show good
agreement with a dynamical multi-mode simulation and allow us to reconstruct
the Wigner function of the spin-squeezed condensate. The techniques
demonstrated here could be directly applied in chip-based atomic clocks which
are currently being set up.

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The categories of this paper are: q-alg
12
The categories of this paper are: nucl-th
14
The categories of this paper are: math-ph
34
The categories of this paper are: chem-ph
10
The categories of this paper are: q-bio
17
The categories of this paper are: q-fin
15
The categories of this paper are: nucl-ex
6
The categories of this paper are: astro-ph
8
The categories of this paper are: hep-ex
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The categories of this paper are: eess
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The categories of this paper are: bayes-an
9
The categories of this paper are: nlin
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The categories of this paper are: supr-con
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The categories of this paper are: cmp-lg
16
The categories of this paper are: stat
24
The categories of this paper are: dg-ga