Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A coherent nanomechanical oscillator driven by single-electron
  tunnelling   A single-electron transistor incorporated as part of a nanomechanical
resonator represents an extreme limit of electron-phonon coupling. While it
allows for fast and sensitive electromechanical measurements, it also
introduces backaction forces from electron tunnelling which randomly perturb
the mechanical state. Despite the stochastic nature of this backaction, under
conditions of strong coupling it is predicted to create self-sustaining
coherent mechanical oscillations. Here, we verify this prediction using
time-resolved measurements of a vibrating carbon nanotube transistor. This
electromechanical oscillator has intriguing similarities with a laser. The
single-electron transistor, pumped by an electrical bias, acts as a gain medium
while the resonator acts as a phonon cavity. Despite the unconventional
operating principle, which does not involve stimulated emission, we confirm
that the output is coherent, and demonstrate other laser behaviour including
injection locking and frequency narrowing through feedback.

12
The categories of this paper are: nucl-th
20
The categories of this paper are: acc-phys
5
The categories of this paper are: gr-qc
22
The categories of this paper are: chao-dyn
13
The categories of this paper are: quant-ph
18
The categories of this paper are: econ
11
The categories of this paper are: hep-lat
7
The categories of this paper are: hep-th
24
The categories of this paper are: dg-ga
6
The categories of this paper are: astro-ph
21
The categories of this paper are: adap-org
14
The categories of this paper are: math-ph
33
The categories of this paper are: plasm-ph
16
The categories of this paper are: stat
36
The categories of this paper are: cmp-lg
9
The categories of this paper are: nlin