Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Laser threshold magnetometry   We propose a new type of sensor, which uses diamond containing the optically
active nitrogen-vacancy (NV$^-$) centres as a laser medium. The magnetometer
can be operated at room-temperature and generates light that can be readily
fibre coupled, thereby permitting use in industrial applications and remote
sensing. By combining laser pumping with a radio-frequency Rabi-drive field, an
external magnetic field changes the fluorescence of the NV$^-$ centres. We use
this change in fluorescence level to push the laser above threshold, turning it
on with an intensity controlled by the external magnetic field, which provides
a coherent amplification of the readout signal with very high contrast. This
mechanism is qualitatively different from conventional NV$^-$--based
magnetometers which use fluorescence measurements, based on incoherent photon
emission. We term our approach laser threshold magnetometry (LTM). We predict
that an NV$^-$--based laser threshold magnetometer with a volume of 1mm$^3$ can
achieve shot-noise limited d.c.~sensitivity of 1.86 fT$/\sqrt{\rm{Hz}}$ and
a.c.~sensitivity of 3.97fT$/\sqrt{\rm{Hz}}$.

27
The categories of this paper are: comp-gas
26
The categories of this paper are: bayes-an
8
The categories of this paper are: hep-ex
33
The categories of this paper are: plasm-ph
0
The categories of this paper are: hep-ph
14
The categories of this paper are: math-ph
28
The categories of this paper are: alg-geom
19
The categories of this paper are: eess
20
The categories of this paper are: acc-phys
1
The categories of this paper are: cs
11
The categories of this paper are: hep-lat
30
The categories of this paper are: q-alg
6
The categories of this paper are: astro-ph
34
The categories of this paper are: chem-ph
17
The categories of this paper are: q-fin
18
The categories of this paper are: econ