Sample-Based Krylov Quantum Diagonalization for the Schwinger Model on Trapped-Ion and Superconducting Quantum Processors

• URL: http://arxiv.org/abs/2510.26951v1
• Date: Thu, 30 Oct 2025 19:21:06 GMT
• Title: Sample-Based Krylov Quantum Diagonalization for the Schwinger Model on Trapped-Ion and Superconducting Quantum Processors
• Authors: Emil Otis Rosanowski, Jurek Eisinger, Lena Funcke, Ulrich Poschinger, Ferdinand Schmidt-Kaler,
• Abstract summary: We apply the recently proposed Sample-based Krylov Quantum Diagonalization (SKQD) method to lattice gauge theories.<n>We study the dependence of the ground-state energy and particle number on the value of the $theta$-term, accurately capturing the model's phase structure.<n>We show that SKQD substantially reduces the effective Hilbert space, and although the Krylov space dimension still scales exponentially, the slower growth underscores its promise for simulating lattice gauge theories in larger volumes.
• Score: 26.315169722500556
• License: http://creativecommons.org/licenses/by/4.0/
• Abstract: We apply the recently proposed Sample-based Krylov Quantum Diagonalization (SKQD) method to lattice gauge theories, using the Schwinger model with a $\theta$-term as a benchmark. SKQD approximates the ground state of a Hamiltonian, employing a hybrid quantum-classical approach: (i) constructing a Krylov space from bitstrings sampled from time-evolved quantum states, and (ii) classically diagonalizing the Hamiltonian within this subspace. We study the dependence of the ground-state energy and particle number on the value of the $\theta$-term, accurately capturing the model's phase structure. The algorithm is implemented on trapped-ion and superconducting quantum processors, demonstrating consistent performance across platforms. We show that SKQD substantially reduces the effective Hilbert space, and although the Krylov space dimension still scales exponentially, the slower growth underscores its promise for simulating lattice gauge theories in larger volumes.

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