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Updated: May 11, 2026
11:03
An Analog Macroscopic Technique for Studying Molecular Hydrodynamic Processes in Dense Gases and Liquids
Published on: December 4, 2017
Microscopic origin of thermodynamic entropy in isolated systems
J M Deutsch1, Haibin Li, Auditya Sharma
1Department of Physics, University of California, Santa Cruz, California 95064, USA.
Summary
Researchers derived a new quantum entropy formula for pure states from wave function self-entanglement. This formula aligns with thermodynamic measurements and von Neumann
Area of Science:
- Quantum Information Theory
- Statistical Mechanics
- Thermodynamics
Background:
- The standard definition of quantum entropy (von Neumann entropy) quantifies information loss and is zero for pure quantum states.
- Thermodynamic experiments measure entropy, but reconciling these measurements with quantum mechanics for pure states has been challenging.
Purpose of the Study:
- To derive a novel formula for quantum entropy of pure states directly from their intrinsic properties.
- To establish a connection between the quantum mechanical concept of self-entanglement and thermodynamic entropy measurements.
- To extend Boltzmann's hypothesis, which links microscopic properties to macroscopic thermodynamics, into the quantum realm.
Main Methods:
- Derivation of a new entropy formula based on the self-entanglement of a quantum system's wave function.
- Numerical simulations to compute entropy for various quantum states (energy eigenstates and time-evolved states).
- Comparison of the newly derived entropy formula with the established von Neumann entropy for nonintegrable systems.
Main Results:
- A new formula for quantum entropy of pure states was successfully obtained, relying solely on wave function self-entanglement.
- Strong numerical evidence shows agreement between the new entropy formula and von Neumann entropy for nonintegrable systems.
- This agreement holds for both energy eigenstates and states evolving over long times from general initial conditions.
Conclusions:
- The study provides a new perspective on quantum entropy, linking it directly to the self-entanglement of pure states.
- The findings suggest a quantum mechanical foundation for thermodynamic entropy measurements in certain systems.
- This work extends classical statistical mechanics principles to the quantum domain, unifying microscopic and thermodynamic descriptions.
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