This study advances the theoretical understanding of decoherence mechanisms in open quantum systems by modelling entanglement dynamics under localised environmental interactions relevant to emerging quantum technologies in Tunisia. A unified analytical framework is developed that bridges Markovian and non-Markovian regimes, quantifying the resilience of bipartite entanglement against structured environmental noise. Considering a system of two non-interacting qubits coupled to a common bosonic reservoir, a generalised master equation incorporating a memory kernel is derived from a structured spectral density function with tunable ohmicity. An analytical expression for the time-dependent concurrence is obtained for an initial Bell state, revealing a crossover from monotonic decay to oscillatory behaviour with entanglement revivals as the reservoir cutoff frequency is lowered relative to the qubit splitting. In the sub-ohmic regime, entanglement decay is slower and revivals are more pronounced, demonstrating that the spectral density cutoff frequency acts as a control parameter for entanglement preservation. The framework incorporates a local noise temperature parameter to represent cryostat fluctuations typical of Tunisian laboratory conditions, allowing the model to capture the phenomenology of entanglement evolution under constraints of limited cryogenic infrastructure and higher ambient noise levels. Crucially, the results show that standard Markovian models systematically overestimate the rate of entanglement loss, particularly in sub-ohmic environments, and that non-Markovian memory effects can temporarily restore quantum correlations after periods of apparent death. These findings challenge the assumption that decoherence is irreversible, revealing a form of quantum memory that could be harnessed for error correction or state protection. The framework provides a practical tool for predicting coherence lifetimes in solid-state and photonic systems, offering a comparative benchmark for experimental platforms within Tunisia's nascent quantum optics community and informing the design of robust quantum information protocols in the North African research context.
This study advances the theoretical understanding of decoherence mechanisms in open quantum systems by modelling entanglement dynamics under localised environmental interactions relevant to emerging quantum technologies in Tunisia. A unified analytical framework is developed that bridges Markovian and non-Markovian regimes, quantifying the resilience of bipartite entanglement against structured environmental noise. Considering a system of two non-interacting qubits coupled to a common bosonic reservoir, a generalised master equation incorporating a memory kernel is derived from a structured spectral density function with tunable ohmicity. An analytical expression for the time-dependent concurrence is obtained for an initial Bell state, revealing a crossover from monotonic decay to oscillatory behaviour with entanglement revivals as the reservoir cutoff frequency is lowered relative to the qubit splitting. In the sub-ohmic regime, entanglement decay is slower and revivals are more pronounced, demonstrating that the spectral density cutoff frequency acts as a control parameter for entanglement preservation. The framework incorporates a local noise temperature parameter to represent cryostat fluctuations typical of Tunisian laboratory conditions, allowing the model to capture the phenomenology of entanglement evolution under constraints of limited cryogenic infrastructure and higher ambient noise levels. Crucially, the results show that standard Markovian models systematically overestimate the rate of entanglement loss, particularly in sub-ohmic environments, and that non-Markovian memory effects can temporarily restore quantum correlations after periods of apparent death. These findings challenge the assumption that decoherence is irreversible, revealing a form of quantum memory that could be harnessed for error correction or state protection. The framework provides a practical tool for predicting coherence lifetimes in solid-state and photonic systems, offering a comparative benchmark for experimental platforms within Tunisia's nascent quantum optics community and informing the design of robust quantum information protocols in the North African research context.
This study presents the first comprehensive dataset on quantum entanglement dynamics in open quantum systems, recorded under the environmental noise profiles characteristic of the Tanzanian equatorial region between 2021 and 2022. The experimental apparatus, situated at the University of Dar es Salaam, employed spontaneous parametric down-conversion in a type-II beta-barium borate crystal to generate polarisation-entangled photon pairs. Tunable spectral filters and liquid-crystal variable retarders were used to engineer controlled Markovian and non-Markovian phase-damping channels, replicating diverse environmental conditions. The dataset comprises 48 CSV files systematically organised across three distinct reservoir spectral densities—Ohmic, sub-Ohmic, and super-Ohmic—each examined under varying coupling strengths. Time-stamped records of concurrence, purity, and negativity, along with associated uncertainties, provide a multi-metric characterisation of the system's state, enabling the disentanglement of genuine quantum correlations from classical mixing effects. A separate metadata file details experimental parameters including system–reservoir coupling constants, temperature, cut-off frequencies, and calibration constants. Data validation was performed through systematic comparison with exact analytical predictions for the Markovian limit, where observed decay curves for concurrence and logarithmic negativity showed high qualitative agreement with theoretical expectations, particularly in the early-time regime. This concordance confirms the integrity of the experimental apparatus and state-reconstruction protocol. The dataset enables validation of theoretical decoherence models under variable thermal and magnetic field fluctuations, offering a benchmark for quantum information processing in resource-limited settings. By systematically cataloguing entanglement evolution under both Markovian and non-Markovian regimes, the data support further research into error mitigation strategies and the development of robust quantum protocols for emerging quantum technologies.
We investigate qubit entanglement dynamics in a two-qubit cavity system with stochastically fluctuating coupling strength, comparing white noise (Markovian) and Ornstein-Uhlenbeck noise (non-Markovian) processes. We analytically solve the system dynamics for both Fock and coherent cavity states and systematically characterize how initial qubit configurations affect entanglement generation and preservation. Our results reveal distinct dynamical regimes: in the Fock-state cavity, initial states in the single-excitation subspace generate robust qubit entanglement in decoherence-free subspaces, while initially entangled states in the double-excitation subspace exhibit inevitable decay without protective symmetries. For coherent cavities, we identify a critical photon-number threshold in the intermediate coherent-state amplitude regime where dynamics transition from low-frequency to high-frequency entanglement oscillations, while universal entanglement loss occurs at large amplitudes. Remarkable resilience against entanglement sudden death emerges under strong non-Markovian noise with long correlation times, where repeated revivals occur. These findings establish cavity photon statistics and environmental memory time as key control parameters for engineering qubit entanglement dynamics in qubit-cavity systems, revealing how system-environment correlations govern quantum information preservation.
Quantum dots are nanometer-scale semiconductor particles that exhibit size-dependent quantum mechanical properties. In this work, we investigate the dynamics of quantum correlations, quantified by the concurrence and the quantum coherence, in a bipartite system of coupled double quantum dots. The analysis is carried out within both Markovian and non-Markovian regimes, and further extended to different noisy quantum channels, including amplitude damping, phase flip, and phase damping. Our results show that environmental memory plays a crucial role in the preservation of quantum correlations, leading to oscillatory behavior and partial revivals in the non-Markovian regime, in contrast to the monotonic decay observed under Markovian dynamics. Moreover, distinct decoherence mechanisms induce qualitatively different effects: dissipative channels rapidly suppress correlations, while phase-based channels lead to either redistribution or gradual degradation. A key finding is that quantum coherence exhibits a higher robustness compared to entanglement under all considered conditions, highlighting its relevance as a reliable quantum resource in noisy environments. These results provide valuable insights into the control and protection of quantum correlations in realistic solid-state systems.
This review consolidates theoretical and experimental progress on quantum entanglement within open systems, with a particular focus on research conducted in Kenya between 2021 and 2022. It critically synthesises local efforts to model decoherence in noisy environments, offering a unified framework that bridges Markovian and non-Markovian dynamics. The work further identifies key challenges in maintaining entanglement under realistic conditions, thereby providing a foundational reference for future experimental quantum information initiatives in the region. The mathematical description of open quantum systems is examined through the Lindblad master equation and Kraus operator formalism, classifying decoherence into dephasing, dissipation, and collective noise. Striking phenomena such as entanglement sudden death, sudden birth, and revivals are explored, alongside experimental validation on trapped-ion and photonic qubit platforms. A thematic analysis addresses non-Markovian memory effects, which can delay entanglement loss through coherence backflow, and evaluates protection strategies including dynamical decoupling, decoherence-free subspaces, and quantum error correction. The suitability of entanglement measures such as concurrence and negativity for assessing these strategies is discussed. A conspicuous research gap is the near absence of experimental quantum laboratories in East Africa; Kenya lacks infrastructure for trapped-ion or superconducting qubit experiments. This deficit motivates the development of low-cost entangled photon sources based on spontaneous parametric down-conversion using continuous-wave diode lasers, which could support fundamental decoherence studies and proof-of-principle demonstrations of entanglement-based quantum key distribution. Underexplored areas include entanglement in biological systems, hybrid quantum-classical networks, and resource-efficient error mitigation techniques. Theoretically, Kenyan physicists are well positioned to develop open-system models incorporating local environmental conditions, bridging the gap between theoretical elegance and experimental feasibility in resource-constrained settings.
Abstract Entanglement is an essential resource for quantum information processing; however, it is highly susceptible to decoherence induced by environmental interactions. In this work, we investigate the entanglement dynamics of a two-qubit system subjected to Markovian noise and explore the effectiveness of external control fields in preserving quantum correlations. Using the Lindblad master equation, we model the evolution of the system under two decoherence channels, namely, amplitude damping (spontaneous emission) and phase damping (dephasing). We introduce periodic driving and optimal control protocols to mitigate entanglement loss and analyze their impact using concurrence as a quantifier of two-qubit entanglement. Our numerical results reveal certain conditions under which sudden death of entanglement can be delayed or even prevented. Additionally, in the case of the initial state being a mixed state, we identify time regimes where entanglement revival occurs, providing insights into quantum error correction strategies. The results contribute to the broader understanding of quantum coherence preservation and have implications for quantum computing, secure quantum communication, and quantum memory design.
Entanglement in continuous-variable Gaussian systems is a key resource, and common reservoirs can both suppress and generate correlations. Existing work focused on pre-entangled states or Markovian baths, leaving open whether separable squeezed inputs entangle in structured environments or under modulation. We study two bosonic modes coupled to a common reservoir, each initialized in a separable squeezed vacuum. Dynamics are analyzed utilizing Gaussian covariance methods, evolved under approximate Non-Markovian quantum state diffusion (QSD), finite-temperature pseudomode embeddings, and Bures-based non-Markovian diagnostics. We identify three mechanisms absent in Markovian dynamics: (1) A detuning condition that freezes entanglement trajectories across reservoir correlation times; (2) birth, death, and revival of entanglement from orthogonal inputs; and (3) integer-locked beating with square-wave oscillations produced by periodic detuning. All mechanisms persist at finite temperature, with deviations bounded within 5% in cryogenic regimes and 20% at moderate occupations. These deviation bounds align with cryogenic cavity, phononic, and optomechanical platforms, where structured spectral densities and detuning modulation are already accessible. Structured reservoirs are shown to emerge as tunable entanglement resources for continuous-variable quantum technologies.