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Generation and Coherent Control of Pulsed Quantum Frequency Combs
Published on: June 8, 2018
Ehrenfest dynamics is purity non-preserving: a necessary ingredient for decoherence
J L Alonso1, J Clemente-Gallardo, J C Cuchí
1Departamento de Física Teórica, Universidad de Zaragoza, Pedro Cerbuna 12, E-50009 Zaragoza, Spain.
The Journal of Chemical Physics
|August 17, 2012
Summary
This study introduces a new framework to track quantum purity changes in statistical Ehrenfest dynamics. It shows how quantum states evolve from pure to mixed based on time, quantum state space dimension, and classical trajectory number.
Area of Science:
- Quantum Dynamics
- Theoretical Chemistry
- Computational Physics
Background:
- Accurately simulating nonadiabatic dynamics in mixed quantum/classical systems is challenging due to the difficulty in defining initial conditions.
- The Ehrenfest model provides a framework for such simulations, but its statistical extension is crucial for realistic systems.
- Purity is a key indicator of quantum state evolution, reflecting the transition from a pure to a mixed state.
Purpose of the Study:
- To develop a novel theoretical framework for calculating the exact change in quantum subsystem purity within the statistical Ehrenfest formalism.
- To investigate how quantum purity evolves in statistical Ehrenfest dynamics, particularly the transition from pure to mixed states.
- To analyze the dependence of purity evolution on key system parameters like time, quantum state space dimension (D), and the number of classical trajectories (N).
Main Methods:
- Utilized the previously established statistical Ehrenfest formalism (Alonso et al., 2011).
- Developed a new analytical framework to precisely determine purity changes during the system's evolution.
- Conducted numerical simulations on a simplified system to verify the theoretical predictions.
Main Results:
- Demonstrated numerically that statistical Ehrenfest dynamics can drive an initially pure quantum state towards a mixed state.
- Quantified the evolution of purity, showing its dependence on time, the dimension of the quantum state space (D), and the number of classical trajectories (N).
- The study provides a method to exactly track purity changes in complex quantum systems.
Conclusions:
- The statistical Ehrenfest formalism accurately describes the decoherence process, leading to a mixed quantum state from an initially pure one.
- The rate and extent of purity evolution are controllable by system parameters (D and N), offering insights into decoherence mechanisms.
- This work opens new avenues for studying decoherence and quantum effects in complex molecular systems using Ehrenfest dynamics.
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