Exploring Entanglement and Parameter Sensitivity in QAOA through Quantum Fisher Information

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Main Authors: Sarmina, Brian García, Benavides, Jorge Saavedra, Sun, Guo-Hua, Dong, Shi-Hai
Format: Preprint
Published: 2025
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author Sarmina, Brian García
Benavides, Jorge Saavedra
Sun, Guo-Hua
Dong, Shi-Hai
author_facet Sarmina, Brian García
Benavides, Jorge Saavedra
Sun, Guo-Hua
Dong, Shi-Hai
contents Quantum Fisher Information (QFI) can be used to quantify how sensitive a quantum state reacts to changes in its variational parameters, making it a natural diagnostic for algorithms such as the Quantum Approximate Optimization Algorithm (QAOA). We perform a systematic QFI analysis of QAOA for Max-Cut on cyclic and complete graphs with $N = 4 - 10$ qubits. Two mixer families are studied, RX-only and hybrid RX-RY, with depths $p = 2, 4, 6$ and $p = 3, 6, 9$, respectively, and with up to three entanglement stages implemented through cyclic- or complete-entangling patterns. Complete graphs consistently yield larger QFI eigenvalues than cyclic graphs; none of the settings reaches the Heisenberg limit ($4N^2$), but several exceed the linear bound ($4N$). Introducing entanglement primarily redistributes QFI from diagonal to off-diagonal entries: non-entangled circuits maximize per-parameter (diagonal) sensitivity, whereas entangling layers increase the covariance fraction and thus cross-parameter correlations, with diminishing returns beyond the first stage. Leveraging these observations, we propose, as a proof of concept, a QFI-Informed Mutation (QIm) heuristic that sets mutation probabilities and step sizes from the normalized diagonal QFI. On 7- and 10-qubit instances, QIm attains higher mean energies and lower variance than equal-probability and random-restart baselines over 100 runs, underscoring QFI as a lightweight, problem-aware preconditioner for QAOA and other variational quantum algorithms.
format Preprint
id arxiv_https___arxiv_org_abs_2507_18844
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Exploring Entanglement and Parameter Sensitivity in QAOA through Quantum Fisher Information
Sarmina, Brian García
Benavides, Jorge Saavedra
Sun, Guo-Hua
Dong, Shi-Hai
Quantum Physics
Emerging Technologies
81P68, 68Q09, 68Q12
I.m; H.m
Quantum Fisher Information (QFI) can be used to quantify how sensitive a quantum state reacts to changes in its variational parameters, making it a natural diagnostic for algorithms such as the Quantum Approximate Optimization Algorithm (QAOA). We perform a systematic QFI analysis of QAOA for Max-Cut on cyclic and complete graphs with $N = 4 - 10$ qubits. Two mixer families are studied, RX-only and hybrid RX-RY, with depths $p = 2, 4, 6$ and $p = 3, 6, 9$, respectively, and with up to three entanglement stages implemented through cyclic- or complete-entangling patterns. Complete graphs consistently yield larger QFI eigenvalues than cyclic graphs; none of the settings reaches the Heisenberg limit ($4N^2$), but several exceed the linear bound ($4N$). Introducing entanglement primarily redistributes QFI from diagonal to off-diagonal entries: non-entangled circuits maximize per-parameter (diagonal) sensitivity, whereas entangling layers increase the covariance fraction and thus cross-parameter correlations, with diminishing returns beyond the first stage. Leveraging these observations, we propose, as a proof of concept, a QFI-Informed Mutation (QIm) heuristic that sets mutation probabilities and step sizes from the normalized diagonal QFI. On 7- and 10-qubit instances, QIm attains higher mean energies and lower variance than equal-probability and random-restart baselines over 100 runs, underscoring QFI as a lightweight, problem-aware preconditioner for QAOA and other variational quantum algorithms.
title Exploring Entanglement and Parameter Sensitivity in QAOA through Quantum Fisher Information
topic Quantum Physics
Emerging Technologies
81P68, 68Q09, 68Q12
I.m; H.m
url https://arxiv.org/abs/2507.18844