# Quantum discord in spin systems with dipole–dipole interaction

Quantum discord in spin systems with dipole–dipole interaction The behavior of total quantum correlations (discord) in dimers consisting of dipolar-coupled spins 1/2 are studied. We found that the discord $$Q=0$$ Q = 0 at absolute zero temperature. As the temperature $$T$$ T increases, the quantum correlations in the system increase at first from zero to its maximum and then decrease to zero according to the asymptotic law $$T^{-2}$$ T - 2 . It is also shown that in absence of external magnetic field $$B$$ B , the classical correlations $$C$$ C at $$T\rightarrow 0$$ T → 0 are, vice versa, maximal. Our calculations predict that in crystalline gypsum $$\hbox {CaSO}_{4}\cdot \hbox {2H}_{2}{\hbox {O}}$$ CaSO 4 · 2H 2 O the value of natural $$(B=0)$$ ( B = 0 ) quantum discord between nuclear spins of hydrogen atoms is maximal at the temperature of 0.644  $$\upmu$$ μ K, and for 1,2-dichloroethane $$\hbox {H}_{2}$$ H 2 ClC– $$\hbox {CH}_{2}{\hbox {Cl}}$$ CH 2 Cl the discord achieves the largest value at $$T=0.517~\upmu$$ T = 0.517 μ K. In both cases, the discord equals $$Q\approx 0.083$$ Q ≈ 0.083  bit/dimer what is $$8.3\,\%$$ 8.3 % of its upper limit in two-qubit systems. We estimate also that for gypsum at room temperature $$Q\sim 10^{-18}$$ Q ∼ 10 - 18  bit/dimer, and for 1,2-dichloroethane at $$T=90$$ T = 90  K the discord is $$Q\sim 10^{-17}$$ Q ∼ 10 - 17  bit per a dimer. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Quantum Information Processing Springer Journals

# Quantum discord in spin systems with dipole–dipole interaction

, Volume 12 (11) – Aug 9, 2013
19 pages

/lp/springer_journal/quantum-discord-in-spin-systems-with-dipole-dipole-interaction-7LWKaQctSS
Publisher
Springer US
Subject
Physics; Quantum Information Technology, Spintronics; Quantum Computing; Data Structures, Cryptology and Information Theory; Quantum Physics; Mathematical Physics
ISSN
1570-0755
eISSN
1573-1332
D.O.I.
10.1007/s11128-013-0617-6
Publisher site
See Article on Publisher Site

### References

• Einselection and decoherence from information theory perspective
Zurek, WH

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