Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Stimulated resonant spin amplification reveals millisecond electron spin
  coherence time of rare-earth ions in solids   The inhomogeneity of an electron spin ensemble as well as fluctuating
environment acting upon individual spins drastically shorten the spin coherence
time $T_2$ and hinder coherent spin manipulation. We show that this problem can
be solved by the simultaneous application of a radiofrequency (rf) field, which
stimulates coherent spin precession decoupled from an inhomogeneous
environment, and periodic optical pulses, which amplify this precession. The
resulting resonance, taking place when the rf field frequency approaches the
laser pulse repetition frequency, has a width determined by the spin coherence
time $T_2$ that is free from the inhomogeneity effects. We measure a
50-Hz-narrow electron spin resonance and milliseconds-long $T_2$ for electrons
in the ground state of Ce$^{3+}$ ions in the YAG lattice at low temperatures,
while the inhomogeneous spin dephasing time $T_2^*$ is only 25 ns. This study
paves the way to coherent optical manipulation in spin systems decoupled from
their inhomogeneous environment.

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The categories of this paper are: hep-th
32
The categories of this paper are: atom-ph
34
The categories of this paper are: chem-ph
36
The categories of this paper are: cmp-lg
12
The categories of this paper are: nucl-th
18
The categories of this paper are: econ
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The categories of this paper are: nlin
20
The categories of this paper are: acc-phys
2
The categories of this paper are: math
31
The categories of this paper are: ao-sci
30
The categories of this paper are: q-alg
14
The categories of this paper are: math-ph
10
The categories of this paper are: q-bio
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The categories of this paper are: eess
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The categories of this paper are: cs
29
The categories of this paper are: funct-an