Entanglement scaling can shift from power law to logarithmic

Hatem Barghathi and Adrian Del Maestro of the University of Tennessee have demonstrated a shift in how entanglement scales with system size, revealing it can transition from a power law to logarithmic growth as the Rényi index changes. The researchers generalized findings from simpler spin models to interacting fermions, a fundamental particle type, suggesting this behavior may be more common than previously understood.They introduced a symmetry-aware lower bound on the von Neumann entropy, constructed from charge-resolved Rényi entropies, offering a protocol for diagnosing anomalous entanglement scaling from experimentally accessible data. This new method could bypass the need for difficult full state tomography in quantum systems.This surprising result, detailed in Quantum, challenges the common assumption that the second Rényi entropy reliably mirrors the behavior of the more difficult-to-measure von Neumann entropy. Previous work focused on simplified systems, but this research reveals the transition isn’t limited to those cases.

The team’s work generalizes findings, showing that even in systems with interacting fermions, fundamental particles exhibiting distinct behaviors from those in simpler spin models, entanglement scaling can undergo this change.They discovered that rare particle-number sectors can mask substantial entanglement, causing the second Rényi entropy to grow logarithmically while the von Neumann entropy expands at a much faster rate. This discrepancy highlights the limitations of relying solely on the second Rényi entropy as a proxy for the von Neumann entropy in quantifying entanglement, and this new approach potentially circumvents the need for full state tomography, a computationally intensive process.The method allows scientists to identify instances where the second Rényi entropy underestimates the true entanglement scaling, providing a more accurate assessment of quantum correlations within a system. Analytical tools are now more readily available to explore the scaling of multipartite entanglement in free-fermion systems.This discrepancy arises because rare configurations with specific particle numbers can dominate the second Rényi entropy calculation, masking the true entanglement present in more common states. This generalization is significant because it suggests the observed entanglement scaling transition may be more widespread than initially believed.They demonstrated this with a specific quantum state, showing that even when the second Rényi entropy indicates limited entanglement, the underlying von Neumann entropy can be significantly larger. This work builds on earlier investigations, including those by Arildsen et al. (2026) on symmetry-resolved entanglement, and opens new avenues for probing complex quantum systems.Specifically, the researchers constructed a number-conserving many-body state where the scaling of entanglement demonstrably changes as the Rényi index is varied, highlighting the index-dependent nature of this phenomenon. They revealed that the scaling of the von Neumann and Rényi entropies can differ, even within the same system. This new approach offers bypassing the need for computationally expensive full state tomography.Quantifying entanglement, a hallmark of quantum systems, remains a significant challenge for both theoretical modeling and experimental verification. While the von Neumann entropy is the gold standard for measuring entanglement, its calculation demands complete knowledge of a system’s quantum state, a process known as full state tomography, which quickly becomes intractable as system size increases. Researchers are therefore often compelled to rely on approximations, most commonly the second Rényi entropy, under the assumption it faithfully reflects the von Neumann entropy’s scaling behavior.However, new work from the University of Tennessee challenges this long-held assumption. Hatem Barghathi and Adrian Del Maestro demonstrated that the relationship between these two measures isn’t always straightforward, even within a seemingly simple system. This means that in certain scenarios, the second Rényi entropy can significantly underestimate the true level of entanglement captured by the von Neumann entropy.👉 More information🗞 Detection of a Rényi Index Dependent Transition in Entanglement Entropy Scaling✍️ Hatem Barghathi and Adrian Del Maestro🧠 DOI: https://quantum-journal.org/papers/q-2026-08-07-2184/See today’s quantum computing news on Quantum Zeitgeist for the latest breakthroughs in qubits, hardware, algorithms, and industry deals.The Quant possesses over two decades of experience in start-up ventures and financial arenas, brings a unique and insightful perspective to the quantum computing sector. This extensive background combines the agility and innovation typical of start-up environments with the rigor and analytical depth required in finance. Such a blend of skills is particularly valuable in understanding and navigating the complex, rapidly evolving landscape of quantum computing and quantum technology marketplaces. The quantum technology marketplace is burgeoning, with immense growth potential. This expansion is not just limited to the technology itself but extends to a wide array of applications in different industries, including finance, healthcare, logistics, and more.