This paper presents a comprehensive investigation of quantum correlations in radiative-capture reactions through a unified lens of quantum information theory and nuclear physics. By combining density matrix formulations with open quantum system dynamics, we can establish universal scaling laws governing the relationship between quantum discord (D), entanglement entropy (S), and fundamental nuclear properties. The analysis reveals the inverse power-law dependencies [Formula: see text] and [Formula: see text] between these quantum metrics and the decay width (Γ), maintained across fourteen nuclear systems spanning six decades in Γ and masses [Formula: see text]. A machine learning architecture that integrates physical constraints with deep residual networks achieves 92% prediction accuracy for coherence lengths [Formula: see text] while identifying shell structure effects that enhance quantum correlations near magic numbers. The persistent quantum discord ([Formula: see text]) observed in systems with sub-attometer coherence lengths suggests nuclear spins maintain non-classical correlations through internal degrees of freedom rather than spatial coherence. The developed phase diagram categorizes nuclear reactions into three quantum technology regimes: memory ([Formula: see text] s[Formula: see text]), sensing ([Formula: see text] s[Formula: see text]), and foundational tests ([Formula: see text] s[Formula: see text]), with [Formula: see text]Fe[Formula: see text] and [Formula: see text]Li[Formula: see text] identified as optimal candidates for applications. These results bridge nuclear physics with quantum information science, providing both theoretical insights into decoherence mechanisms and practical tools for quantum material design. The proposed methodology establishes radiative capture reactions as a novel platform for exploring emergent quantum phenomena in strongly interacting systems.
This paper presents a comprehensive investigation of quantum correlations in radiative-capture reactions through a unified lens of quantum information theory and nuclear physics. By combining density matrix formulations with open quantum system dynamics, we can establish universal scaling laws governing the relationship between quantum discord (D), entanglement entropy (S), and fundamental nuclear properties. The analysis reveals the inverse power-law dependencies [Formula: see text] and [Formula: see text] between these quantum metrics and the decay width (Γ), maintained across fourteen nuclear systems spanning six decades in Γ and masses [Formula: see text]. A machine learning architecture that integrates physical constraints with deep residual networks achieves 92% prediction accuracy for coherence lengths [Formula: see text] while identifying shell structure effects that enhance quantum correlations near magic numbers. The persistent quantum discord ([Formula: see text]) observed in systems with sub-attometer coherence lengths suggests nuclear spins maintain non-classical correlations through internal degrees of freedom rather than spatial coherence. The developed phase diagram categorizes nuclear reactions into three quantum technology regimes: memory ([Formula: see text] s[Formula: see text]), sensing ([Formula: see text] s[Formula: see text]), and foundational tests ([Formula: see text] s[Formula: see text]), with [Formula: see text]Fe[Formula: see text] and [Formula: see text]Li[Formula: see text] identified as optimal candidates for applications. These results bridge nuclear physics with quantum information science, providing both theoretical insights into decoherence mechanisms and practical tools for quantum material design. The proposed methodology establishes radiative capture reactions as a novel platform for exploring emergent quantum phenomena in strongly interacting systems.
Coherence length ([Formula: see text]) is a key concept in quantum mechanics, representing the ability of a quantum system to maintain well-defined phase relationships over time. This paper investigates the relationship between coherence length, decay width (Γ), and atomic mass in radiative capture reactions using a machine learning model. Additionally, the quantum entanglement of the resulting states is quantified using the von Neumann entropy. The results demonstrate the inverse relationship between coherence length and decay width, highlighting the universal nature of this relationship across various reactions. The findings provide valuable insights into the behavior of particles in radiative capture reactions and have implications for both experimental and theoretical studies in nuclear and particle physics.
Quantum resource theories allow us to quantify a useful quantum phenomenon, to develop new protocols for its detection and determine the exact processes that maximize its use for practical tasks. These theories aim at transforming physical phenomena, such as entanglement and quantum coherence, into useful properties for the execution of concrete tasks related to quantum information. In this thesis, we focus on the resource theories of entanglement, discord-like quantum correlations, and quantum coherence, the most intriguing quantum phenomena exploited so far in quantum information theory. We begin by presenting in detail the theoretical tools of these quantum resources, focusing on the most remarkable techniques and computational problems. In this sense, we discuss several mathematical methods that solve some problems related to their quantifications, and some analytical results for bipartite quantum systems are given. We also examine the intrinsic connections between these quantum resources by extracting the links that unite the corresponding measures. In contrast, the revolution of quantum technology has led to a growing interest in quantum metrology, and quantum entanglement has been employed to overcome the classical limit in several quantum estimation protocols. In this work, we analyze the role of quantum correlations beyond entanglement in improving the accuracy of an unknown parameter. According to our results, correlations can be captured using quantum Fisher information, and quantum discord correlations can be exploited to ensure the accuracy of phase estimation protocols. This thesis includes also the contributions on the dynamics of these quantum resources in various models of open quantum systems. Among our objectives, is to study the effects of the environment on these quantum resources and to obtain techniques to protect them from the effects of intrinsic decoherence.
Measurements of quantum systems disturb their states. To quantify this nonclassical characteristic, Zurek and Ollivier [Phys. Rev. Lett. 88, 017901 (2001)] introduced the quantum discord, a quantum correlation that can be nonzero even when entanglement in the system is zero. Discord has aroused great interest as a resource that is more robust against the effects of decoherence and offers the exponential speed-up of certain computational algorithms. Here, we study general two-level bipartite systems and give general results on the relationship between discord, entanglement, and linear entropy. We also identify the states for which discord takes a maximal value for a given entropy or entanglement, thus placing strong bounds on entanglement-discord and entropy-discord relations. We find out that although discord and entanglement are identical for pure states, they differ when generalized to mixed states as a result of the difference in the method of generalization.
Two quantum states with identical entanglement, two neural networks with identical parameters, and two mass superpositions with identical constituents—in each case, one survives while the other is destroyed.We identify the single geometric variable that controls information survival across all three. For decades, information stability in quantum systems and machine learning has been analyzed through resource counting—particle number, entanglement magnitude, or parameter count—despite persistent, model-independent failures of these explanations. The most prominent examples are the exponential fragility of GHZ states relative to Cluster states under identical decoherence and the frequent breakdown of transfer in overparameterized neural networks. These phenomena were observed, quantified, and repeatedly labeled "surprising," yet no controlling variable or mechanism was identified. This work provides both. We identify a geometric invariant—the spectral bottleneck D*—and show that it induces a concrete mechanism of information loss: spectral peeling, in which coherence decays shell-by-shell in order of increasing spectral distance from the noise geometry. From first principles, we prove that under general Markovian dynamics the entropy gap obeys the asymptotic decay law D_M(t) = A · W_{≤D}(t) + O(W^{3/2})**, where D controls the decay exponent and the Kubo-Mori prefactor A controls the thermodynamic response. This yields the parameter-free prediction τ_Cluster/τ_GHZ = n, verified on IBM quantum hardware with sub-percent agreement, and predicts robustness inversions under correlated noise invisible to all entanglement measures. The framework extends in three directions: (i) to non-Markovian dynamics, where the static noise metric is replaced by an integrated metric Σ_d(t) = ∫₀ᵗ Σ_k γ_k(s) d_k ds and the bottleneck D* is preserved exactly; (ii) to machine learning, where the same structure governs transfer fidelity under domain shift; and (iii) to gravitational decoherence, where GHZ-like mass superpositions collapse as n² while cluster-like configurations remain robust, yielding a 10⁸× discriminant test between gravitational and environmental collapse. The conclusion is a structural principle: information persists when encoded at minimal spectral distance from the noise geometry. Noise destroys outer shells first—spectral peeling—and the innermost occupied shell controls survival.
We investigate evolution of quantum correlations in ensembles of two-qubit nuclear spin systems via nuclear magnetic resonance techniques. We use discord as a measure of quantum correlations and the Werner state as an explicit example. We, first, introduce different ways of measuring discord and geometric discord in two-qubit systems and then describe the following experimental studies: (a) We quantitatively measure discord for Werner-like states prepared using an entangling pulse sequence. An initial thermal state with zero discord is gradually and periodically transformed into a mixed state with maximum discord. The experimental and simulated behavior of rise and fall of discord agree fairly well. (b) We examine the efficiency of dynamical decoupling sequences in preserving quantum correlations. In our experimental setup, the dynamical decoupling sequences preserved the traceless parts of the density matrices at high fidelity. But they could not maintain the purity of the quantum states and so were unable to keep the discord from decaying. (c) We observe the evolution of discord for a singlet-triplet mixed state during a radio-frequency spin-lock. A simple relaxation model describes the evolution of discord, and the accompanying evolution of fidelity of the long-lived singlet state, reasonably well.
This paper develops a comprehensive theoretical framework for designing quantum memory systems with enhanced resilience to thermal decoherence through engineered lattice geometries and protective structures. We formulate a unified mathematical description connecting material properties, geometric configurations, and quantum information retention capabilities, establishing design principles for long-lived quantum states. The theory begins with a detailed analysis of decoherence mechanisms in structured quantum materials, deriving analytical expressions for coherence time as functions of lattice topology, defect engineering, and environmental coupling strength. We prove theoretical bounds on achievable memory lifetimes under various physical constraints and identify optimal geometric configurations that maximize information retention. The framework incorporates both passive protection mechanisms-arising from intrinsic material properties and geometric shielding-and active stabilization strategies involving periodic error detection and correction. We establish scaling laws that predict how memory performance varies with system size, temperature, and structural parameters, providing design guidelines for practical implementations. Our analysis reveals fundamental trade-offs between memory density, access time, and coherence preservation, offering a theoretical roadmap for next-generation quantum memory architectures. This work bridges quantum information theory, condensed matter physics, and materials science to advance understanding of thermally resilient quantum storage.