Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A Low-Noise High-Density Alkali Metal Scalar Magnetometer   We present an experimental and theoretical study of a scalar atomic
magnetometer using an oscillating field-driven Zeeman resonance in a
high-density optically-pumped potassium vapor. We describe an experimental
implementation of an atomic gradiometer with a noise level below 10
fT/Hz^{1/2}, fractional field sensitivity below 10^{-9}/Hz^{1/2}, and an active
measurement volume of about 1.5 cm^3. We show that the fundamental field
sensitivity of a scalar magnetometer is determined by the rate of alkali-metal
spin-exchange collisions even though the resonance linewidth can be made much
smaller than the spin-exchange rate by pumping most atoms into a stretched spin
state.

37
The categories of this paper are: supr-con
5
The categories of this paper are: gr-qc
4
The categories of this paper are: cond-mat
11
The categories of this paper are: hep-lat
0
The categories of this paper are: hep-ph
26
The categories of this paper are: bayes-an
34
The categories of this paper are: chem-ph
2
The categories of this paper are: math
18
The categories of this paper are: econ
15
The categories of this paper are: nucl-ex
31
The categories of this paper are: ao-sci
8
The categories of this paper are: hep-ex
13
The categories of this paper are: quant-ph
14
The categories of this paper are: math-ph
36
The categories of this paper are: cmp-lg
35
The categories of this paper are: mtrl-th