Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Scrambling and quantum feedback in a nanomechanical system   The question of how swiftly entanglement spreads over a system has attracted
vital interest. In this regard, the out-of-time ordered correlator (OTOC) is a
quantitative measure of the entanglement spreading process. Particular interest
concerns the propagation of quantum correlations in the lattice systems, {\it
e.g.}, spin chains. In a seminal paper D. A. Roberts, D. Stanford and L.
Susskind, J. High Energy Phys. 03, 051, (2015) the concept of the OTOC's radius
was introduced. The radius of the OTOC defines the front line reached by the
spread of entanglement. Beyond this radius operators commute. In the present
work, we propose a model of two nanomechanical systems coupled with two
Nitrogen-vacancy (NV) center spins. Oscillators are coupled to each other
directly while NV spins are not. Therefore, the correlation between the NV
spins may arise only through the quantum feedback exerted from the first NV
spin to the first oscillator and transferred from the first oscillator to the
second oscillator via the direct coupling. Thus nonzero OTOC between NV spins
quantifies the strength of the quantum feedback. We show that NV spins cannot
exert quantum feedback on classical nonlinear oscillators. We also discuss the
inherently quantum case with a linear quantum harmonic oscillator indirectly
coupling the two spins and verify that in the classical limit of the
oscillator, the OTOC vanishes.

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The categories of this paper are: econ
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The categories of this paper are: chem-ph
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The categories of this paper are: astro-ph
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The categories of this paper are: math
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The categories of this paper are: q-fin
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The categories of this paper are: math-ph
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The categories of this paper are: hep-ph
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The categories of this paper are: q-alg
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The categories of this paper are: physics
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The categories of this paper are: bayes-an
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The categories of this paper are: cs
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The categories of this paper are: acc-phys
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The categories of this paper are: stat
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The categories of this paper are: cond-mat
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The categories of this paper are: ao-sci
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The categories of this paper are: nucl-ex