• DOI:10.1103/PhysRevLett.117.130401
• Corpus ID: 21543860

Quantum Correlations, Separability, and Quantum Coherence Length in Equilibrium Many-Body Systems.

@article{Malpetti2016QuantumCS,
  title={Quantum Correlations, Separability, and Quantum Coherence Length in Equilibrium Many-Body Systems.},
  author={Daniele Malpetti and Tommaso Roscilde},
  journal={Physical review letters},
  year={2016},
  volume={117 13},
  pages={
          130401
        }
}

• D. Malpetti, T. Roscilde
• Published 13 May 2016
• Physics
• Physical review letters

Nonlocality is a fundamental trait of quantum many-body systems, both at the level of pure states, as well as at the level of mixed states. Because of nonlocality, mixed states of any two subsystems are correlated in a stronger way than what can be accounted for by considering the correlated probabilities of occupying some microstates. In the case of equilibrium mixed states, we explicitly build two-point quantum correlation functions, which capture the specific, superior correlations of quantum systems at finite temperature, and which are directly accessible to experiments when correlating measurable properties. When nonvanishing, these correlation functions rule out a precise form of separability of the equilibrium state. In particular, we show numerically that quantum correlation functions generically exhibit a finite quantum coherence length, dictating the characteristic distance over which degrees of freedom cannot be considered as separable. This coherence length is completely disconnected from the correlation length of the system-as it remains finite even when the correlation length of the system diverges at finite temperature-and it unveils the unique spatial structure of quantum correlations.