Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: How much work can a quantum device extract from a heat engine?   Work extraction from a heat engine in a cycle by a quantum mechanical device
(quantum "piston") is analyzed. The standard definition of work fails in the
quantum domain. The correct extractable work and its efficiency bound are shown
to crucially depend on the initial quantum state of the piston. The transient
efficiency bound may exceed the standard Carnot bound, although it complies
with the second law. Energy gain (e.g. in lasing) is shown to drastically
differ from work gain.

28
The categories of this paper are: alg-geom
26
The categories of this paper are: bayes-an
22
The categories of this paper are: chao-dyn
18
The categories of this paper are: econ
17
The categories of this paper are: q-fin
30
The categories of this paper are: q-alg
16
The categories of this paper are: stat
6
The categories of this paper are: astro-ph
12
The categories of this paper are: nucl-th
24
The categories of this paper are: dg-ga
8
The categories of this paper are: hep-ex
36
The categories of this paper are: cmp-lg
7
The categories of this paper are: hep-th
25
The categories of this paper are: patt-sol
20
The categories of this paper are: acc-phys
27
The categories of this paper are: comp-gas