Dynamics of quantum correlations in colored-noise environments

Abstract

We address the dynamics of entanglement and quantum discord for two noninteracting qubits initially prepared\ud in a maximally entangled state and then subjected to a classical colored noise, i.e., coupled with an external\ud environment characterized by a noise spectrum of the form 1/f α.More specifically, we address systems in which\ud the Gaussian approximation fails, i.e., mere knowledge of the spectrum is not enough to determine the dynamics\ud of quantum correlations. We thus investigate the dynamics for two different configurations of the environment:\ud in the first case, the noise spectrum is due to the interaction of each qubit with a single bistable fluctuator with\ud an undetermined switching rate, whereas in the second case we consider a collection of classical fluctuators with\ud fixed switching rates. In both cases, we found analytical expressions for the time dependence of entanglement\ud and quantum discord, which may also be extended to a collection of fluctuators with random switching rates.\ud The environmental noise is introduced by means of stochastic time-dependent terms in the Hamiltonian, and this\ud allows us to describe the effects of both separate and common environments. We show that the non-Gaussian\ud character of the noise may lead to significant effects, e.g., environments with the same power spectrum, but\ud different configurations give rise to the opposite behavior for quantum correlations. In particular, depending\ud on the characteristics of the environmental noise considered, both entanglement and discord display either a\ud monotonic decay or the phenomena of sudden death and revivals. Our results show that the microscopic structure\ud of the environment, in addition to its noise spectrum, is relevant for the dynamics of quantum correlations and\ud may be a valid starting point for the engineering of non-Gaussian colored environments

Non-Markovianity of colored noisy channels

“…A stochastic process is non-Gaussian if it cannot be fully characterized by the mean and variance. As a consequence, the mere knowledge of the spectrum is not sufficient to describe the process, and the very structure of environment plays a role in determining its influence on the coherence properties of quantum systems [29].…”

Distributed correlations and information flows within a hybrid multipartite quantum-classical system

“…The utilization of quantum correlations, like entanglement, nonlocality, and discord, is in fact jeopardized by the detrimental effects of the environment surrounding the quantum system [6][7][8][9][10][11][12] so that finding strategies to preserve them has become a main requirement. Non-Markovian noise, originating from structured environments or from strong couplings [4][5][6]13], has been shown to enable dynamical revivals of quantum correlations independently of the quantum [8,[14][15][16][17] or classical [18][19][20][21][22][23][24][25][26][27][28][29][30][31] nature of the environment, allowing an extension of their exploitation time. It is therefore of basic interest to understand the origin of these revival phenomenons.…”

Data-pattern tomography of entangled states

“…Thus, the criterion of the required accuracy of the representation can be expressed as F (ρ, ρ Appr ) ≥ 0.999. Notice that states that are close in terms of fidelity may have rather different physical properties, as has been shown theoretically and experimentally, for example, in [28][29][30]. So, when judging the quality of the state representation, we estimate also purity and the entanglement.…”