Variational preparation of quantum many-body scars with shallow circuits
Year: 2026
Type: article
Abstract: We present and benchmark a type of variational quantum eigensolver (VQE) which we denote σ -VQE. It is designed to target midspectrum eigenstates and prepare quantum many-body scar states. The approach leverages the fact that noisy intermediate-scale quantum devices are limited in their ability to generate generic highly entangled states. This modified VQE pairs a low-depth circuit with an energy-selective objective that explicitly penalizes energy variance around a chosen target energy. The cost function exploits the limited expressibility of the shallow circuit as atypical low-entanglement eigenstates such as scar states are preferentially selected. We validate this mechanism across two complementary families of models that contain many-body scar states: the Shiraishi-Mori embedding approach and a matrix product state parent Hamiltonian construction. We define an unbiased estimation scheme for the nonlinear cost function that is compatible with qubit-wise commuting grouping and bitstring reuse. A proof-of-principle demonstration using a small-system instance was performed on IBM Fez in December 2025 (Heron r2 QPU). These results motivate its use as a practical algorithm for detecting quantum many-body scars and variationally generating states with appreciable scar state overlap.
Source: Physical Review A
DOI: 10.1103/5l8p-42fv
Language: English
Subfield: Artificial Intelligence
Field: Computer Science
Domain: Physical Sciences
Open Access status: hybrid
Estimated APC paid: $2,675
Awards: G103507813, G1105844351, G1175115578, G1536341141, G1690208154, G1722358650, G178676023, G2019505627, G2105336002, G2262748287, G300979063, G3480869486, G3592681187, G410571670, G425668148, G451917667, G4692141684, G491712853, G5080475149, G5209569390, G5539308778, G5967599077, G6033112984, G7084143925, G7805626310, G7863371703, G8497050386, G8575212178
OpenAlex ID: W7165039666