Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A simple quantum heat engine   Quantum heat engines employ as working agents multi-level systems instead of
gas-filled cylinders. We consider particularly two-level agents such as
electrons immersed in a magnetic field. Work is produced in that case when the
electrons are being carried from a high-magnetic-field region into a
low-magnetic-field region. In watermills, work is produced instead when some
amount of fluid drops from a high-altitude reservoir to a low-altitude
reservoir. We show that this purely mechanical engine may in fact be considered
as a two-level quantum heat engine, provided the fluid is viewed as consisting
of n molecules of weight one and N-n molecules of weight zero. Weight-one
molecules are analogous to electrons in their higher energy state, while
weight-zero molecules are analogous to electrons in their lower energy state.
More generally, fluids consist of non-interacting molecules of various weights.
It is shown that, not only the average value of the work produced per cycle,
but also its fluctuations, are the same for mechanical engines and quantum
(Otto) heat engines. The reversible Carnot cycles are approached through the
consideration of multiple sub-reservoirs.

36
The categories of this paper are: cmp-lg
9
The categories of this paper are: nlin
26
The categories of this paper are: bayes-an
28
The categories of this paper are: alg-geom
18
The categories of this paper are: econ
12
The categories of this paper are: nucl-th
10
The categories of this paper are: q-bio
8
The categories of this paper are: hep-ex
11
The categories of this paper are: hep-lat
6
The categories of this paper are: astro-ph
22
The categories of this paper are: chao-dyn
24
The categories of this paper are: dg-ga
1
The categories of this paper are: cs
0
The categories of this paper are: hep-ph
21
The categories of this paper are: adap-org
37
The categories of this paper are: supr-con