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Dissipative quantum dynamics with the surrogate Hamiltonian approach. A comparison between spin and harmonic baths
David Gelman1, Christiane P Koch, Ronnie Kosloff
1Fritz Haber Research Center for Molecular Dynamics, Hebrew University of Jerusalem, Jerusalem, 91904, Israel.
The Journal of Chemical Physics
|July 21, 2004
Summary
This study compares spin and harmonic baths for anharmonic oscillators. Spin baths can saturate energy acceptance, but interactions spread excitation, while entanglement primarily occurs in spin baths.
Area of Science:
- Quantum Dynamics
- Condensed Matter Physics
- Quantum Information
Background:
- Understanding quantum system dissipation is crucial.
- Anharmonic oscillators exhibit complex behaviors when coupled to external environments.
- Distinguishing between different bath types (spin vs. harmonic) is key for accurate modeling.
Purpose of the Study:
- To investigate and differentiate the dissipative quantum dynamics of an anharmonic oscillator coupled to spin and harmonic baths.
- To analyze the impact of bath properties on system relaxation and entanglement.
- To compare the surrogate Hamiltonian approach with the multiconfiguration time-dependent Hartree method.
Main Methods:
- Utilized the surrogate Hamiltonian approach for spin bath simulations, constructing a finite system-bath Hamiltonian.
- Employed the multiconfiguration time-dependent Hartree method for harmonic bath calculations.
- Analyzed convergence with respect to bath mode excitations and compared results in weak and strong coupling regimes.
Main Results:
- Both methods converge to the Markovian limit in the weak coupling regime at zero temperature for small system excitations.
- Spin baths exhibit saturation in energy acceptance for highly excited systems, which can be mitigated by bath mode interactions.
- Phase loss between cat states shows similar behavior for both bath types, but dynamics deviate at stronger couplings.
- Entanglement generation between bath modes is observed exclusively in the spin bath dynamics.
Conclusions:
- The choice of bath significantly influences quantum dissipative dynamics, particularly at higher excitation levels and stronger couplings.
- The surrogate Hamiltonian approach provides accurate results for spin baths, comparable to established methods for harmonic baths.
- Spin baths uniquely facilitate the generation of entanglement within the bath itself, offering distinct quantum properties.