Abstract In this paper, we investigate the decoherence of qubit due to its coupling to a Hermitian or a non-Hermitian environment within the pure dephasing spin-boson model. Using this model, we analytically establish the previously anticipated similarity between the non-equilibrium and the equilibrium correlation functions $P_x(t)$ and $C_x(t)$ . We find that integer values of $A$ (coupling strength) or $s$ (bath exponent) has distinctive long time asymptotic behaviors of $P_x(t)$ and $C_x(t)$ from those of the non-integer values, accompanied with a diverging crossover time scale. We also find that the non-Hermitian environment tends to suppress the decoherence of qubit for all values of $A$ and $s$ , in contrast to the conclusion of Dey et al . [Phys. Lett. A 383, 125931 (2019)]. Our results show the potential of the non-Hermitian environmental engineering for suppressing the decoherence of qubit.Abstract In this paper, we investigate the decoherence of qubit due to its coupling to a Hermitian or a non-Hermitian environment within the pure dephasing spin-boson model. Using this model, we analytically establish the previously anticipated similarity between the non-equilibrium and the equilibrium correlation functions $P_x(t)$ and $C_x(t)$. We find that integer values of $A$ (coupling strength) or $s$ (bath exponent) has distinctive long time asymptotic behaviors of $P_x(t)$ and $C_x(t)$ from those of the non-integer values, accompanied with a diverging crossover time scale. We also find that the non-Hermitian environment tends to suppress the decoherence of qubit for all values of $A$ and $s$, in contrast to the conclusion of Dey et al . [Phys. Lett. A 383, 125931 (2019)]. Our results show the potential of the non-Hermitian environmental engineering for suppressing the decoherence of qubit.

Chinese Physics BMar 12, 20260 citations

The equilibrium state of the spin Boson model

M. Fannes, Bruno Nachtergaele, André F. Verbeure

Jan 1, 19882 citations

Non-equilibrium quantum dynamics of the magnetic Anderson model

D Becker, S Weiss, Michael Thorwart +1 more

We study the non-equilibrium dynamics of a spinful single-orbital quantum dot with an incorporated quantum mechanical spin-1/2 magnetic impurity. Due to the spin degeneracy, double occupancy is allowed, and Coulomb interaction together with the exchange coupling of the magnetic impurity influence the dynamics. By extending the iterative summation of real-time path integrals (ISPI) to this coupled system, we monitor the time-dependent non-equilibrium current and the impurity spin polarization to determine features of the time-dependent non-equilibrium dynamics. We particulary focus on the deep quantum regime, where all time and energy scales are of the same order of magnitude and no small parameter is available. We observe a significant influence of the non-equilibrium decay of the impurity spin polarization both in the presence and in the absence of Coulomb interaction. The exponential relaxation is faster for larger bias voltages, electron–impurity interactions and temperatures. We show that the exact relaxation rate deviates from the corresponding perturbative result. In addition, we study in detail the impurity's back action on the charge current and find a reduction of the stationary current for increasing coupling to the impurity. Moreover, our approach allows us to systematically distinguish mean-field Coulomb and impurity effects from the influence of quantum fluctuations and flip-flop scattering, respectively. In fact, we find a local maximum of the current for a finite Coulomb interaction due to the presence of the impurity.We study the non-equilibrium dynamics of a spinful single-orbital quantum dot with an incorporated quantum mechanical spin-1/2 magnetic impurity. Due to the spin degeneracy, double occupancy is allowed, and Coulomb interaction together with the exchange coupling of the magnetic impurity influence the dynamics. By extending the iterative summation of real-time path integrals (ISPI) to this coupled system, we monitor the time-dependent non-equilibrium current and the impurity spin polarization to determine features of the time-dependent non-equilibrium dynamics. We particulary focus on the deep quantum regime, where all time and energy scales are of the same order of magnitude and no small parameter is available. We observe a significant influence of the non-equilibrium decay of the impurity spin polarization both in the presence and in the absence of Coulomb interaction. The exponential relaxation is faster for larger bias voltages, electron–impurity interactions and temperatures. We show that the exact relaxation rate deviates from the corresponding perturbative result. In addition, we study in detail the impurity's back action on the charge current and find a reduction of the stationary current for increasing coupling to the impurity. Moreover, our approach allows us to systematically distinguish mean-field Coulomb and impurity effects from the influence of quantum fluctuations and flip-flop scattering, respectively. In fact, we find a local maximum of the current for a finite Coulomb interaction due to the presence of the impurity.

arXiv:1205.2462New Journal of PhysicsJul 26, 201210 citations

The equilibrium thermodynamics of a spin-boson model

John T. Lewis, G. A. Raggio

Journal of Statistical PhysicsMar 1, 19889 citations

The equilibrium states of the spin-boson model

M. Fannes, Bruno Nachtergaele, André F. Verbeure

Communications in Mathematical PhysicsDec 1, 198858 citations

P_x(t)

and

C_x(t)

. We find that integer values of

A

(coupling strength) or

s

(bath exponent) has distinctive long time asymptotic behaviors of

P_x(t)

and

C_x(t)

from those of the non-integer values, accompanied with a diverging crossover time scale. We also find that the non-Hermitian environment tends to suppress the decoherence of qubit for all values of

A

and

s

, in contrast to the conclusion of Dey et al . [Phys. Lett. A 383, 125931 (2019)]. Our results show the potential of the non-Hermitian environmental engineering for suppressing the decoherence of qubit.