Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Quantum discord in spin systems with dipole-dipole interaction   The behavior of total purely quantum correlation (discord) in dimers
consisting of dipolar-coupled spins 1/2 is studied. We found that the discord
Q=0 at the absolute zero temperature. With increasing the temperature $T$, at
first the quantum correlations in the system increase, smoothly reach the
maximum, and then turn again into zero according to the asymptotic law
$T^{-2}$. It is also shown that in absence of external magnetic field $B$, the
classical correlation $C$ at $T\to0$ is, vice versa, maximal. Our calculations
predict that in crystalline gypsum ${\rm CaSO_4\cdot2H_2O}$ the value of
natural (B=0) quantum discord between nuclear spins of hydrogen atoms is
maximal at the temperature of 0.644 $\mu$K, and for 1,2-dichloroethane ${\rm
H_2ClC-CH_2Cl}$ the discord achieves the largest value at $T=0.517 \mu$K. In
both cases, the discord equals $Q\approx0.083$ bit/dimer what is 8.3% of its
upper limit in two-qubit systems. We estimate also that for gypsum at room
temperature $Q\sim10^{-18}$ bit/dimer, and for 1,2-dichloroethane at T=90 K the
discord is $Q\sim10^{-17}$ bit per a dimer.

37
The categories of this paper are: supr-con
36
The categories of this paper are: cmp-lg
4
The categories of this paper are: cond-mat
25
The categories of this paper are: patt-sol
19
The categories of this paper are: eess
30
The categories of this paper are: q-alg
20
The categories of this paper are: acc-phys
2
The categories of this paper are: math
27
The categories of this paper are: comp-gas
9
The categories of this paper are: nlin
0
The categories of this paper are: hep-ph
5
The categories of this paper are: gr-qc
17
The categories of this paper are: q-fin
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The categories of this paper are: adap-org
26
The categories of this paper are: bayes-an
7
The categories of this paper are: hep-th