HEP Lattice·hep-lat

Mon·Aug 24, 2026Monday·August 24, 2026

4 papers—1 primary·3 cross-listed

01
Exponential-in- $N_{c}^{2}$ cost reduction of product-formula-based quantum simulations of quantum chromodynamics
Zohreh Davoudi🇺🇸 · Jesse R. Stryker🇺🇸
Quantum algorithms for simulating quantum chromodynamics (QCD) have matured steadily since the pioneering work of Byrnes and Yamamoto [PRA 73, 022328 (2006)]. The most popular strategies for Hamiltonian simulation involve product-formula decompositions. However, the application of product-formula methods to SU( $N_{c}$ ) lattice gauge theories by Byrnes and Yamamoto leads to $O (Λ^{8 (N_{c}^{2} - 1)})$ gate complexity per Trotter step, where $Λ$ is the bosonic cutoff in the electric (i.e., irreducible-representation) basis. A seminal work by Kan and Nam [arXiv:2107.12769 (2021)] significantly improves over such an undesirable cost and reports an $O (Λ polylog (Λ))$ scaling, yet it still calls for an unrealistically large number of quantum gates. Here, we illuminate one of the reasons behind this high cost estimate and show that a factor of size $O (2^{4 (N_{c}^{2} - 1)})$ can be removed from the per-Trotter-step cost estimate by Kan and Nam. We specifically show that, by using methods developed in our past works [PRD 112, 014508 (2025); Quantum 7, 1213 (2023)], exponentiated-Hamiltonian decomposition---a necessary step in the application of product-formula algorithms---can be performed far more efficiently than previously thought. Our method reduces the T-gate cost estimate of QCD simulations using a second-order product formula by a factor of nearly $1 0^{14}$ , independent of simulation parameters and sizes. Focusing on simulations in the electric basis, we further contrast our results with other methods: the local-multiplet basis approach of Ciavarella, Klco, and Savage [PRD 103, 094501 (2021)] and the near-optimal algorithm of Rhodes, Kreshchuk, and Pathak [PRX Quantum 5, 040347 (2024)]. This work highlights the importance of continued algorithmic improvement to bringing the quantum-simulation cost of QCD within reach of realistic quantum computers.
hep-lathep-phnucl-thquant-ph1 citation
02
Poles in $π N$ scattering from forward dispersion relations and revised total cross-section data
José Ramón Peláez🇪🇸 · Pablo Rabán🇪🇸 · Jacobo Ruiz de Elvira🇪🇸
We present a model-independent calculation of $π N$ forward dispersion relations and their analytic continuation to the complex plane, using a revised set of $π^{\pm} p$ total cross-section data up to 3 GeV, and Regge asymptotics above. Up to that energy, we find four stable poles for each isospin combination. The lightest pole in the $I = 3/2$ channel corresponds to the $Δ (1232)$ resonance, while the lightest in the $I = 1/2$ channel corresponds to the Roper resonance, even though the latter is imperceptible in the data. We extract their pole parameters and the parameter difference between the $Δ^{0}$ and $Δ^{++}$ , without relying on a partial-wave analysis. The remaining poles cannot be identified with a single resonance each. They are not artifacts but the combined effect of multiple resonances unresolved by total cross-section data alone. Finally, we write sum rules relating the residues of these constituent resonances to the residues of the poles extracted from the dispersive representation.
↳ hep-phhep-exhep-latnucl-th0 citations
03
The excited baryon spectrum from a unified quark model
Yan-Ke Chen🇨🇳 · Liang-Zhen Wen🇨🇳 · Wei-Lin Wu🇨🇳 · Lu Meng🇨🇳 · Shi-Lin Zhu🇨🇳
A common approach to studying the multiquark states is to solve the few-body Schrödinger equation within a quark potential model. The multiquark states may contain quarks with several different flavors and have richer color structures than ordinary hadrons. The reliability of such an investigation requires that the underlying quark potential model can simultaneously describe the meson and baryon spectra across all flavor sectors, including orbital and radial excitations, with a single parameter set. At present, no quark potential model fully satisfies this requirement. We construct a simple nonrelativistic constituent quark potential model that includes spin--orbit and tensor interactions. We refit the model parameters to the latest experimental data. The excited light hadrons and several exotic hadron candidates are excluded from the fit. The resulting parameter set reproduces the spectra across all fitted sectors. The vast majority of deviations are below 20 MeV, while the largest deviations remain of the order of several tens of MeV, which is the typical accuracy of nonrelativistic quark potential models. Using the same parameters, we predict the spectra and internal structures of the orbitally and radially excited heavy baryons, which await further experimental determination. The excited light baryons are calculated with the same parameters. The calculated excited light baryon spectra deviate substantially from experimental values. Our refitted model does not resolve these longstanding discrepancies. The results delimit the range of validity of the nonrelativistic constituent quark potential model. By treating mesons and baryons across all flavor sectors, including both orbital and radial excitations within a unified framework, the model provides a controlled starting point for few-body calculations of multiquark states. We also urge experimental searches for the predicted states.
↳ hep-phhep-exhep-lat0 citations
04
Symmetry Constrained Quantum Error Mitigation for the Schwinger Model
Alexander Tomlinson🇬🇧 · Graham Van Goffrier🇬🇧 · Bipasha Chakraborty🇬🇧 · Zhenyu Cai🇬🇧
Quantum error mitigation (QEM) is at the very heart of near-term quantum simulations and lattice gauge theories are no exceptions, rather their physical symmetries provide natural consistency checks on noise quantum states. In this work, we exploit the parity and fermion-number symmetries of a gauge theory, the (1+1)-dimensional Schwinger model, under depolarising noise and investigate symmetry verification under digital quantum simulation. We investigate two set-ups - symmetry- sector post-selection in adiabatic state preparation followed by real-time measurements of the chiral condensate and symmetry verification within a variational quantum eigensolver (VQE). In the first case, post-selection reduces the bias in the chiral condensate consistently removing up to 60% of the quantum noise induced error in our system. Motivated by the observed regularity of the residual bias (in the low-noise regime), we further introduce a global-noise calibration obtained from classically accessible smaller lattices and implemented on larger lattices recovering noiseless chiral condensate values within statistical uncertainty. However, in VQE, symmetry verification does not seem to generally improve the optimised parameters or the fidelity of the prepared states, although it reduces the bias in the estimated ground-state energy. This demonstates that improving a noisy cost-function estimator in variational algorithms does not necessarily improve the outcome of the algorithm. Our results show the strength of symmetry verification in different approaches while establishing that its usefulness critically depends on where it is applied in the computational workflow, and provide practical guidance for symmetry-assisted quantum error mitigation in quantum simulations of lattice gauge theories.
↳ quant-phhep-latphysics.comp-ph0 citations

Affiliations

first authorsco-authorsvia INSPIRE

Exponential-in-Nc2​ cost reduction of product-formula-based quantum simulations of quantum chromodynamics

Poles in πN scattering from forward dispersion relations and revised total cross-section data

The excited baryon spectrum from a unified quark model

Symmetry Constrained Quantum Error Mitigation for the Schwinger Model

Affiliations

Exponential-in- $N_{c}^{2}$ cost reduction of product-formula-based quantum simulations of quantum chromodynamics

Poles in $π N$ scattering from forward dispersion relations and revised total cross-section data