Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Saturation of Thermal Complexity of Purification   We purify the thermal density matrix of a free harmonic oscillator as a
two-mode squeezed state, characterized by a squeezing parameter and squeezing
angle. While the squeezing parameter is fixed by the temperature and frequency
of the oscillator, the squeezing angle is otherwise undetermined, so that the
complexity of purification is obtained by minimizing the complexity of the
squeezed state over the squeezing angle. The resulting complexity of the
thermal state is minimized at non-zero values of the squeezing angle and
saturates to an order one number at high temperatures, indicating that there is
no additional operator cost required to build thermal states beyond a certain
temperature. We also review applications in which thermal density matrices
arise for quantum fields on curved spacetimes, including Hawking radiation and
a simple model of decoherence of cosmological density perturbations in the
early Universe. The complexity of purification for these mixed states also
saturates as a function of the effective temperature, which may have
interesting consequences for the quantum information stored in these systems.

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The categories of this paper are: supr-con
15
The categories of this paper are: nucl-ex
30
The categories of this paper are: q-alg
19
The categories of this paper are: eess
0
The categories of this paper are: hep-ph
33
The categories of this paper are: plasm-ph
36
The categories of this paper are: cmp-lg
11
The categories of this paper are: hep-lat
14
The categories of this paper are: math-ph
9
The categories of this paper are: nlin
8
The categories of this paper are: hep-ex
12
The categories of this paper are: nucl-th
26
The categories of this paper are: bayes-an
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The categories of this paper are: adap-org
3
The categories of this paper are: physics
1
The categories of this paper are: cs