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Related Experiment Video

Updated: May 8, 2025

Quantum State Engineering of Light with Continuous-wave Optical Parametric Oscillators

Quantum State Engineering of Light with Continuous-wave Optical Parametric Oscillators

Published on: May 30, 2014

Universal Stochastic Equations of Monitored Quantum Dynamics.

Zhenyu Xiao¹, Tomi Ohtsuki², Kohei Kawabata³

¹Peking University, International Center for Quantum Materials, Beijing 100871, China.

Physical Review Letters

|April 25, 2025

Summary

We found an even-odd effect in quantum purification dynamics. Entropy decays exponentially for even numbers of fermions but algebraically for odd numbers, revealing dynamical criticality.

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Area of Science:

Quantum physics
Statistical mechanics

Background:

Understanding quantum dynamics of mixed states is crucial.
Fokker-Planck equations model stochastic processes.

Purpose of the Study:

Derive universal Fokker-Planck equations for Gaussian mixed states.
Investigate the purification dynamics and entropy evolution.
Classify universality classes of nonunitary quantum dynamics.

Main Methods:

Derivation of universal Fokker-Planck equations.
Exact analytical solutions for density-matrix spectra.
Analysis of entropy decay and fluctuations.
Classification based on fundamental symmetry.

Main Results:

Revealed an even-odd effect in purification dynamics: exponential entropy decay for even N fermions, algebraic decay for odd N.
Identified universal entropy fluctuations in the chaotic regime.
Classified universality classes of nonunitary quantum dynamics.

Conclusions:

The study provides exact solutions for quantum dynamics of Gaussian mixed states.
An even-odd effect in purification dynamics indicates dynamical criticality.
Universality classes of nonunitary dynamics are elucidated and classified.