entanglement entropy
Artificial Entanglement in the Fine-Tuning of Large Language Models
Chen, Min, Wang, Zihan, Chen, Canyu, Wu, Zeguan, Li, Manling, Liu, Junyu
Large language models (LLMs) can be adapted to new tasks using parameter-efficient fine-tuning (PEFT) methods that modify only a small number of trainable parameters, often through low-rank updates. In this work, we adopt a quantum-information-inspired perspective to understand their effectiveness. From this perspective, low-rank parameterizations naturally correspond to low-dimensional Matrix Product States (MPS) representations, which enable entanglement-based characterizations of parameter structure. Thereby, we term and measure "Artificial Entanglement", defined as the entanglement entropy of the parameters in artificial neural networks (in particular the LLMs). We first study the representative low-rank adaptation (LoRA) PEFT method, alongside full fine-tuning (FFT), using LLaMA models at the 1B and 8B scales trained on the Tulu3 and OpenThoughts3 datasets, and uncover: (i) Internal artificial entanglement in the updates of query and value projection matrices in LoRA follows a volume law with a central suppression (termed as the "Entanglement Valley"), which is sensitive to hyper-parameters and is distinct from that in FFT; (ii) External artificial entanglement in attention matrices, corresponding to token-token correlations in representation space, follows an area law with logarithmic corrections and remains robust to LoRA hyper-parameters and training steps. Drawing a parallel to the No-Hair Theorem in black hole physics, we propose that although LoRA and FFT induce distinct internal entanglement signatures, such differences do not manifest in the attention outputs, suggesting a "no-hair" property that results in the effectiveness of low rank updates. We further provide theoretical support based on random matrix theory, and extend our analysis to an MPS Adaptation PEFT method, which exhibits qualitatively similar behaviors.
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Scalable Quantum State Preparation via Large-Language-Model-Driven Discovery
Cao, Qing-Hong, Hou, Zong-Yue, Li, Ying-Ying, Liu, Xiaohui, Song, Zhuo-Yang, Zhang, Liang-Qi, Zhang, Shutao, Zhao, Ke
Efficient quantum state preparation remains a central challenge in first-principles quantum simulations of dynamics in quantum field theories, where the Hilbert space is intrinsically infinite-dimensional. Here, we introduce a large language model (LLM)-assisted framework for quantum-circuit design that systematically scales state-preparation circuits to large lattice volumes. Applied to a 1+1d XY spin chain, the LLM autonomously discovers a compact 4-parameter circuit that captures boundary-induced symmetry breaking with sub-percent energy deviation, enabling successful validation on the \texttt{Zuchongzhi} quantum processor. Guided by this insight, we extend the framework to 2+1d quantum field theories, where scalable variational ansätze have remained elusive. For a scalar field theory, the search yields a symmetry-preserving, 3-parameter shallow-depth ansatz whose optimized parameters converge to size-independent constants for lattices $n \ge 4$, providing, to our knowledge, the first scalable ansatz for this class of 2+1d models. Our results establish a practical route toward AI-assisted, human-guided discovery in quantum simulation.
Quantum Flow Matching
Cui, Zidong, Zhang, Pan, Tang, Ying
The flow matching has rapidly become a dominant paradigm in classical generative modeling, offering an efficient way to interpolate between two complex distributions. We extend this idea to the quantum realm and introduce the Quantum Flow Matching (QFM-a fully quantum-circuit realization that offers efficient interpolation between two density matrices. QFM offers systematic preparation of density matrices and generation of samples for accurately estimating observables, and can be realized on quantum computers without the need for costly circuit redesigns. We validate its versatility on a set of applications: (i) generating target states with prescribed magnetization and entanglement entropy, (ii) estimating nonequilibrium free-energy differences to test the quantum Jarzynski equality, and (iii) expediting the study on superdiffusion. These results position QFM as a unifying and promising framework for generative modeling across quantum systems.
Reinforcement Learning for Optimizing Large Qubit Array based Quantum Sensor Circuits
Attisara, Laxmisha Ashok, Kumar, Sathish
As the number of qubits in a sensor increases, the complexity of designing and controlling the quantum circuits grows exponentially. Manually optimizing these circuits becomes infeasible. Optimizing entanglement distribution in large-scale quantum circuits is critical for enhancing the sensitivity and efficiency of quantum sensors [5], [6]. This paper presents an engineering integration of reinforcement learning with tensor-network-based simulation (MPS) for scalable circuit optimization for optimizing quantum sensor circuits with up to 60 qubits. To enable efficient simulation and scalability, we adopt tensor network methods, specifically the Matrix Product State (MPS) representation, instead of traditional state vector or density matrix approaches. Our reinforcement learning agent learns to restructure circuits to maximize Quantum Fisher Information (QFI) and entanglement entropy while reducing gate counts and circuit depth. Experimental results show consistent improvements, with QFI values approaching 1, entanglement entropy in the 0.8-1.0 range, and up to 90% reduction in depth and gate count. These results highlight the potential of combining quantum machine learning and tensor networks to optimize complex quantum circuits under realistic constraints.
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Sequence-Model-Guided Measurement Selection for Quantum State Learning
Huang, Jiaxin, Zhu, Yan, Chiribella, Giulio, Wu, Ya-Dong
Machine learning provides a powerful tool for characterizing quantum systems based on measurement data [1-40]. In particular, deep neural networks have played an important role across a range of tasks, including quantum state reconstruction [7-16], quantum similarity testing [17, 20, 37], prediction of quantum entanglement [21, 24, 40], and state classification [25-33]. Recent progress has enabled sequence models to predict diverse quantum properties of scalable quantum systems, by modeling the measurement outcome distributions [18, 19, 22, 23, 39, 41]. An important question in quantum state learning is how to choose the appropriate measurements to gather information about an unknown quantum state. While an optimized adaptive choice can be found for small quantum systems [42-44], a full optimization quickly becomes intractable as the size of the system grows large. For scalable quantum systems, a widespread approach is to employ randomized measurements [45-51]. This approach enables the estimation of a wide range of observables without performing a full tomography of the quantum state, which is not feasible for large quantum systems. When prior knowledge is available, the randomized measurement choices can be further optimized [52-54]. In general, however, determining the optimal distributions is computationally challenging for large-scale quantum systems, especially when an approximated classical description is lacking.
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Estimation of the reduced density matrix and entanglement entropies using autoregressive networks
Białas, Piotr, Korcyl, Piotr, Stebel, Tomasz, Zapolski, Dawid
We present an application of autoregressive neural networks to Monte Carlo simulations of quantum spin chains using the correspondence with classical two-dimensional spin systems. We use a hierarchy of neural networks capable of estimating conditional probabilities of consecutive spins to evaluate elements of reduced density matrices directly. Using the Ising chain as an example, we calculate the continuum limit of the ground state's von Neumann and Rényi bipartite entanglement entropies of an interval built of up to 5 spins. We demonstrate that our architecture is able to estimate all the needed matrix elements with just a single training for a fixed time discretization and lattice volume. Our method can be applied to other types of spin chains, possibly with defects, as well as to estimating entanglement entropies of thermal states at non-zero temperature.
Project Alexandria: Towards Freeing Scientific Knowledge from Copyright Burdens via LLMs
Schuhmann, Christoph, Rabby, Gollam, Prabhu, Ameya, Ahmed, Tawsif, Hochlehnert, Andreas, Nguyen, Huu, Heidrich, Nick Akinci, Schmidt, Ludwig, Kaczmarczyk, Robert, Auer, Sören, Jitsev, Jenia, Bethge, Matthias
Paywalls, licenses and copyright rules often restrict the broad dissemination and reuse of scientific knowledge. We take the position that it is both legally and technically feasible to extract the scientific knowledge in scholarly texts. Current methods, like text embeddings, fail to reliably preserve factual content, and simple paraphrasing may not be legally sound. We urge the community to adopt a new idea: convert scholarly documents into Knowledge Units using LLMs. These units use structured data capturing entities, attributes and relationships without stylistic content. We provide evidence that Knowledge Units: (1) form a legally defensible framework for sharing knowledge from copyrighted research texts, based on legal analyses of German copyright law and U.S. Fair Use doctrine, and (2) preserve most (~95%) factual knowledge from original text, measured by MCQ performance on facts from the original copyrighted text across four research domains. Freeing scientific knowledge from copyright promises transformative benefits for scientific research and education by allowing language models to reuse important facts from copyrighted text. To support this, we share open-source tools for converting research documents into Knowledge Units. Overall, our work posits the feasibility of democratizing access to scientific knowledge while respecting copyright.
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Flow-based Sampling for Entanglement Entropy and the Machine Learning of Defects
Bulgarelli, Andrea, Cellini, Elia, Jansen, Karl, Kühn, Stefan, Nada, Alessandro, Nakajima, Shinichi, Nicoli, Kim A., Panero, Marco
We introduce a novel technique to numerically calculate R\'enyi entanglement entropies in lattice quantum field theory using generative models. We describe how flow-based approaches can be combined with the replica trick using a custom neural-network architecture around a lattice defect connecting two replicas. Numerical tests for the $\phi^4$ scalar field theory in two and three dimensions demonstrate that our technique outperforms state-of-the-art Monte Carlo calculations, and exhibit a promising scaling with the defect size.
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A Laplacian-based Quantum Graph Neural Network for Semi-Supervised Learning
Gholipour, Hamed, Bozorgnia, Farid, Hambarde, Kailash, Mohammadigheymasi, Hamzeh, Mancilla, Javier, Sequeira, Andre, Neves, Joao, Proença, Hugo
Laplacian learning method is a well-established technique in classical graph-based semi-supervised learning, but its potential in the quantum domain remains largely unexplored. This study investigates the performance of the Laplacian-based Quantum Semi-Supervised Learning (QSSL) method across four benchmark datasets -- Iris, Wine, Breast Cancer Wisconsin, and Heart Disease. Further analysis explores the impact of increasing Qubit counts, revealing that adding more Qubits to a quantum system doesn't always improve performance. The effectiveness of additional Qubits depends on the quantum algorithm and how well it matches the dataset. Additionally, we examine the effects of varying entangling layers on entanglement entropy and test accuracy. The performance of Laplacian learning is highly dependent on the number of entangling layers, with optimal configurations varying across different datasets. Typically, moderate levels of entanglement offer the best balance between model complexity and generalization capabilities. These observations highlight the crucial need for precise hyperparameter tuning tailored to each dataset to achieve optimal performance in Laplacian learning methods.
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