Speaker
Description
Grokking, the delayed transition from memorization to generalization, is a fundamental phenomenon in gradient-based learning, yet its dynamics within variational quantum machine learning (QML) remain largely unexamined. In this work, we report the empirical observation of both the grokking transition and epoch-wise double descent in a two-qubit quantum neural network (QNN) under a complete parameterization of the SU(4) manifold. We demonstrate that overparameterization via increased circuit depth improves
the probability of successful generalization. Notably, these architectures frequently exhibit an epoch-wise double descent in test error, degrading at a critical epoch before recovering into a generalizing state. Crucially, we identify a generalization decay in late-stage
training, where the test error increases significantly despite a stagnant training loss. Bridging this behavior with algorithmic stability
theory, our analysis reveals that this decay correlates with an unconstrained increase of the weight-norm, drifting away from sparse,
phase-aligned harmonic solutions toward overfitted solutions in the Hilbert space. We analyze the underlying temporal dynamics of
this transition, demonstrating how the onset of generalization is linked to optimization hyperparameters such as learning rate and
weight decay. Finally, to mitigate late-stage decay, we introduce a weak explicit weight-norm regularization into the loss function. We
demonstrate that this structural anchor stabilizes the post-grokking phase and permanently preserves generalization gains, providing a robust framework for training overparameterized quantum circuits.
| Topic | Quantum variational circuits and their applications |
|---|---|
| Additional Topic | Theoretical foundations of quantum learning |