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A Photonic System for Generating Unconditional Polarization-Entangled Photons Based on Multiple Quantum Interference
Published on: September 5, 2019
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Ensemble Inequivalence in Long-Range Quantum Systems
Nicolò Defenu1, David Mukamel2, Stefano Ruffo3
1Institute for Theoretical Physics, <a href="https://ror.org/05a28rw58">ETH Zürich</a>, Wolfgang-Pauli-Strasse 27, 8093 Zürich, Switzerland.
Physical Review Letters
|August 19, 2024
Summary
Ensemble inequivalence, where different statistical ensembles yield varied thermodynamic properties, is shown in a quantum ferromagnet. Unlike short-range systems, this quantum system exhibits distinct phase diagrams at finite temperatures between ensembles.
Area of Science:
- Quantum physics
- Statistical mechanics
- Condensed matter physics
Background:
- Ensemble inequivalence is a known feature of classical long-range physics.
- Thermodynamic properties typically converge across ensembles for macroscopic short-range systems.
Purpose of the Study:
- To demonstrate ensemble inequivalence in a quantum ferromagnet.
- To investigate the behavior of quantum systems with long-range interactions.
Main Methods:
- Analysis of a quantum ferromagnet model.
- Comparison of microcanonical and canonical ensembles.
- Phase diagram analysis at T=0 and finite temperatures.
Main Results:
- The T=0 microcanonical and canonical quantum phase diagrams coincide.
- Significant differences emerge between ensemble phase diagrams at finite temperatures.
- This contrasts with the behavior of short-range interacting systems.
Conclusions:
- Ensemble inequivalence is a characteristic of quantum long-range interacting systems.
- Findings challenge the universality of ensemble equivalence in quantum statistical mechanics.
- Implications for atomic, molecular, and optical systems are discussed.
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