Non-Markovian dynamics is studied for two interacting quibts strongly coupled to a dissipative bosonic environment. For the first time, we have derived the non-Markovian quantum state diffusion (QSD) equation for the coupled two-qubit system without any approximations, and in particular, without the Markov approximation. As an application and illustration of our derived time-local QSD equation, we investigate the temporal behavior of quantum coherence dynamics. In particular, we find a strongly non-Markovian regime where entanglement generation is significantly modulated by the environmental memory. Additionally, we studied the residual entanglement in the steady state by analyzing the steady state solution of the QSD equation. Finally, we have discussed an approximate QSD equation.

We study entanglement dynamics in the presence of correlated environmental noises. Specifically, we investigate the quantum entanglement DYNAMics of two spins in the presence of correlated classical white noises, deriving Markov master equation and obtaining explicit solutions for several interesting classes of initial states including Bell states and X form density matrices. We show how entanglement can be enhanced or reduced by the correlation between the two participating noises.Keywords Entanglement dynamics · Correlated noises · Two-qubit model · Entanglement sudden death PACS 03.67.-a · 03.65.Yz · 03.65.Ud · 03.67.Mn IntroductionMany proposed applications in quantum computing [1], quantum communication [2], and quantum cryptography [3] revolve around harnessing the inherent correlation between quantum particles, called entanglement [4]. Although quantum mechanics dictates that these coherence effects are intrinsic in certain systems, even when the atoms or particles are non-local, there is an overall weakening due to coupling to noisy environments [5] that eventually leads to the fast decay of entanglement [6][7][8][9][10][11][12][13][14][15][16]. As such, the study of the controlled entanglement dynamics is of much B. Corn · T. Yu (B)

ABSTRACT:In the framework of quantum-chemical methods (RHF, MP2, and DFT), we study the reaction of photoinduced isomerization of biological molecules-retinal in rhodopsin (Rh) and bacteriorhodopsin (BRh)-the key intermediates in the vision process. The charge redistribution in the retinal chromophore of these biological molecules as the mechanism of the photoinduced isomerization is investigated. The results of the Mulliken, Löwdin, Natural Bond, and ESP population analyses are compared and validated. We demonstrate that the isomerization reaction is accompanied by the substantial charge relocation within the isomerization region with the electron localization on C11 for the retinal in Rh and C14 for the retinal in BRh.

The fully quantized model of double qubits coupled to a common bath is solved using the quantum state diffusion (QSD) approach in the non-Markovian regime. We have established the explicit time-local non-Markovian QSD equations for the two-qubit dissipative and dephasing models. Diffusive quantum trajectories are applied to the entanglement estimation of two-qubit systems in a non-Markovian regime. In both cases, non-Markovian features of entanglement evolution are revealed through quantum diffusive unravellings in the system state space.