Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Long nuclear spin decay times controlled by optical pumping in
  individual quantum dots   Nuclear polarization dynamics are measured in the nuclear spin bi-stability
regime in a single optically pumped InGaAs/GaAs quantum dot. The controlling
role of nuclear spin diffusion from the dot into the surrounding material is
revealed in pump-probe measurements of the non-linear nuclear spin dynamics. We
measure nuclear spin decay times in the range 0.2-5 sec, strongly dependent on
the optical pumping time. The long nuclear spin decay arises from polarization
of the material surrounding the dot by spin diffusion for long (>5sec) pumping
times. The time-resolved methods allow the detection of the unstable nuclear
polarization state in the bi-stability regime otherwise undetectable in cw
experiments.

33
The categories of this paper are: plasm-ph
11
The categories of this paper are: hep-lat
5
The categories of this paper are: gr-qc
23
The categories of this paper are: solv-int
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The categories of this paper are: chem-ph
36
The categories of this paper are: cmp-lg
25
The categories of this paper are: patt-sol
7
The categories of this paper are: hep-th
20
The categories of this paper are: acc-phys
2
The categories of this paper are: math
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The categories of this paper are: alg-geom
8
The categories of this paper are: hep-ex
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The categories of this paper are: adap-org
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The categories of this paper are: atom-ph
15
The categories of this paper are: nucl-ex
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The categories of this paper are: q-alg