Does temperature favor quantum coherence of a dissipative two-level system?

Abstract

The quantum dynamics of a two-level system coupled to an Ohmic spin- bath is studied by means of the perturbation approach based on a unitary transformation. A scattering function ${\xi }_k$ is introduced in the transformation to take into account quantum fluctuations. By the master equation within the Born approximation, nonequilibrium dynamics quantities are calculated. The method works well for the coupling constant $0<\alpha <{\alpha }_c$ and a finite bare tunneling $\Delta$. It is found that (i) only at zero temperature with small coupling or moderate one does the spin-spin-bath model display identical behavior as the well known spin-boson-bath model; (ii) in comparison with the known results of spin-boson-bath model, the coherence-incoherence transition point, which occurs at ${\alpha }_c=1/2[1+\eta \Delta /{\omega }_c]$, is temperature independent; (iii) the nonequilibrium correlation function $P(t)=<{\tau }_z(t)>$, evolves without temperature dependence while $<{\tau }_x(t)>$ depends on temperature. Both $P(t)$ and $<{\tau }_x(t)>$ not only satisfy their initial conditions, respectively, and also have correct long time limits. Besides, the Shiba's relation and sum rule are exactly satisfied in the coherent regime for this method. Our results show that increasing temperature does not help the system suppress decoherence in the coherent regime, i.e., finite temperature does not favor the coherent dynamics in this regime. Thus, the finite-temperature dynamics induced by two kinds of baths spin-bath and boson-bath exhibit distinctly different physics.

21 pages 4 figures

References in corpus (5)

• Coherent control of a single electron spin with electric fields
• Non-Markovian dynamics in a spin star system: Exact solution and approximation techniques
• Spin Precession and Real Time Dynamics in the Kondo Model: A Time-Dependent Numerical Renormalization-Group Study
• Decoherence and dissipation of a quantum harmonic oscillator coupled to two-level systems
• Dissipative quantum dynamics with the Surrogate Hamiltonian approach. A comparison between spin and harmonic baths

Cited by in corpus (9)

• Local observation of antibunching in a trapped Fermi gas
• Analog control of open quantum systems under arbitrary decoherence
• A Unified Stochastic Formulation of Dissipative Quantum Dynamics. II. Beyond Linear Response of Spin Baths
• Effects of counterrotating interaction on driven tunneling dynamics: coherent destruction of tunneling and Bloch-Siegert shift
• From Zeno to anti-Zeno: decoherence-control dependence on the quantum statistics of the bath
• Two-level system in spin baths: Non-adiabatic dynamics and heat transport
• Effects of counter-rotating-wave terms on the non-Markovianity in quantum open systems
• Bias-modulated dynamics of a strongly driven two-level system
• Non-Markovian Quantum State Diffusion for Spin Environments