Effects of Dephasing and Dissipation on Nonequilibrium Quantum Noise

Niklas Mann, Jochen Brüggemann, Michael Thorwart

Xiang-Ji Cai, Yujun Zheng

We investigate theoretically the dynamical dephasing of a quantum system induced by non-Markovian noise in a nonequilibrium environment. We derive the closed equation of the dephasing factor for the quantum system under the nonstationary non-Markovian dichotomic noise environment. It is shown that the nonequilibrium feature of the environment gives rise to a time-dependent frequency shift and suppresses the dynamical dephasing of the quantum system and the environmental backaction of coherence. The memory effect of the environmental noise can reduce the dynamical dephasing of the quantum system and make the coherent backaction from the environment prominent. The non-Markovian feature of the environment, however, may not result in non-Markovian behavior in the dephasing dynamics of the quantum system.

Saulo H. S. Silva, Gabriel Teixeira Landi, Emmanuel Pereira

In order to reveal mechanisms to control and manipulate spin currents, we perform a detailed investigation of the dephasing effects in the open XX model with a Lindblad dynamics involving global dissipators and thermal baths. Specifically, we consider dephasing noise modeled by current-preserving Lindblad dissipators acting on graded versions of these spin systems, that is, systems in which the magnetic field and/or the spin interaction are growing (decreasing) along the chain. In our analysis, we study the nonequilibrium steady state via the covariance matrix using the Jordan-Wigner approach to compute the spin currents. We find that the interplay between dephasing and graded systems gives rise to a nontrivial behavior: When we have homogeneous magnetic field and graded interactions we have rectification enhancement mechanisms, and when we have fully graded systems we can control the spin current in order to keep the direction of the particle and/or spin flow even with inverted baths. We describe our result in detailed numerical analysis and we see that rectification in this simple model indicates that the phenomenon may generally occur in quantum spin systems.

Y. N. Srivastava, Giuseppe Vitiello, A. Widom

J. C. Garrison, R. Y. Chiao

Marisa Ulfa, Donny Dwiputra

Abstract We investigate how long-range power-law hopping interaction, ∼ 1/r a , affects the characteristics of dissipative quantum transport in a nonequilibrium setting. The model under consideration is a noninteracting bosonic chain subject to thermal baths of differing temperature at its boundaries and dephasing noise which is applied uniformly to all the sites. It is shown that the steady-state current may vary nonmonotonically and has a peak for a finite a depending on the position of the cold bath. This site-specific behaviour stems back to the interference effect caused by the parity of the total sites N and the baths positions. The fractional nature of the system, along with the interplay between coherent and incoherent transport, will affect the steady state current that characterizes the transport.