TITAN: A Trajectory-Informed Technique for Adaptive Parameter Freezing in Large-Scale VQE
This addresses scalability issues in quantum chemistry and materials science simulations by reducing hardware demands for VQE, though it appears incremental as it builds on existing parameter-freezing concepts with a novel deep learning approach.
The paper tackles the training efficiency bottleneck in Variational Quantum Eigensolver (VQE) for large Hamiltonians by proposing Titan, a deep learning framework that identifies and freezes inactive parameters at initialization, achieving up to 3 times faster convergence and 40% to 60% fewer circuit evaluations than state-of-the-art baselines while maintaining accuracy.
Variational quantum Eigensolver (VQE) is a leading candidate for harnessing quantum computers to advance quantum chemistry and materials simulations, yet its training efficiency deteriorates rapidly for large Hamiltonians. Two issues underlie this bottleneck: (i) the no-cloning theorem imposes a linear growth in circuit evaluations with the number of parameters per gradient step; and (ii) deeper circuits encounter barren plateaus (BPs), leading to exponentially increasing measurement overheads. To address these challenges, here we propose a deep learning framework, dubbed Titan, which identifies and freezes inactive parameters of a given ansatze at initialization for a specific class of Hamiltonians, reducing the optimization overhead without sacrificing accuracy. The motivation of Titan starts with our empirical findings that a subset of parameters consistently has a negligible influence on training dynamics. Its design combines a theoretically grounded data construction strategy, ensuring each training example is informative and BP-resilient, with an adaptive neural architecture that generalizes across ansatze of varying sizes. Across benchmark transverse-field Ising models, Heisenberg models, and multiple molecule systems up to 30 qubits, Titan achieves up to 3 times faster convergence and 40% to 60% fewer circuit evaluations than state-of-the-art baselines, while matching or surpassing their estimation accuracy. By proactively trimming parameter space, Titan lowers hardware demands and offers a scalable path toward utilizing VQE to advance practical quantum chemistry and materials science.