arXiv subjects

James W. T. Keeble

Publications and source records attributed to James W. T. Keeble.

3 recordsLinked to original sources

arXiv2026

Features of Non-Local Quantum Correlations in Nuclei

Classical simulation of quantum many-body systems is challenged by the combined effects of entanglement and non-stabilizerness (magic). Non-local magic, $M^{\mathrm{NL}}_α$, quantifies the component of non-stabilizerness that cannot be removed by local unitary transformations and provides a measure of quantum complexity beyond entanglement alone. It is bounded from below by the antiflatness of the entanglement spectrum, ${F}_A$. We calculate stabilizer Rényi entropies, non-local magic, entanglement-spectrum antiflatness, and entanglement entropy in shell-model ground states of more than 260 even-even, odd-even, and odd-odd nuclei, using a bipartition into proton and neutron sectors. We find that the previously established bound $4{F}_A\leq{M}^{\mathrm{NL}}_{\mathrm{lin}}$ holds for every nucleus studied and approaches saturation in the limit of separable states. Odd-odd nuclei exhibit markedly different patterns of entanglement and magic compared with even-even and odd-even systems, revealing distinctive signatures of proton-neutron quantum correlations and providing new insight into the complexity generated by nuclear interactions.

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arXiv2026

Neural Quantum States in Non-Stabilizer Regimes: Benchmarks with Atomic Nuclei

As neural networks are known to efficiently represent classes of tensor-network states as well as volume-law-entangled states, identifying which properties determine the representational capabilities of neural quantum states (NQS) remains an open question. We construct NQS representations of ground states of medium-mass atomic nuclei, which typically exhibit significant entanglement and non-stabilizerness, to study their performance in relation to the quantum complexity of the target state. Leveraging a second-quantized formulation of NQS tailored for nuclear-physics applications, we perform calculations in active orbital spaces using a restricted Boltzmann machine (RBM), a prototypical NQS ansatz. For a fixed number of configurations, we find that states with larger non-stabilizerness are systematically harder to learn, as evidenced by reduced accuracy. This finding suggests that non-stabilizerness is a primary factor governing the compression and representational efficiency of RBMs in entangled regimes, and motivates extending these studies to more sophisticated network architectures.

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arXiv2025

Quantum Magic and Multi-Partite Entanglement in the Structure of Nuclei

Motivated by the Gottesman-Knill theorem, we present a detailed study of the quantum complexity of $p$-shell and $sd$-shell nuclei. Valence-space nuclear shell-model wavefunctions generated by the BIGSTICK code are mapped to qubit registers using the Jordan-Wigner mapping (12 qubits for the $p$-shell and 24 qubits for the $sd$-shell), from which measures of the many-body entanglement ($n$-tangles) and magic (non-stabilizerness) are determined. While exact evaluations of these measures are possible for nuclei with a modest number of active nucleons, Monte Carlo simulations are required for the more complex nuclei. The broadly-applicable Pauli-String $IZ$ exact (PSIZe-) MCMC technique is introduced to accelerate the evaluation of measures of magic in deformed nuclei (with hierarchical wavefunctions), by factors of $\sim 8$ for some nuclei. Significant multi-nucleon entanglement is found in the $sd$-shell, dominated by proton-neutron configurations, along with significant measures of magic. This is evident not only for the deformed states, but also for nuclei on the path to instability via regions of shape coexistence and level inversion. These results indicate that quantum-computing resources will accelerate precision simulations of such nuclei and beyond.

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