Predictive Structure Behind Rare Outcomes in Random Quantum Circuits

Abstract:Rare outputs of random quantum circuits are usually treated as terminal statistics. We ask whether they reveal intermediate organization that remains useful beyond the selecting future. Comparing unconditioned random-normal (RN) and peak-selected random-peaked (RP) circuits from the same local generator, we find stronger pairwise correlations and probability redistribution but reduced bipartite and output spreading in RP across n=8-16. Exact full-suffix decomposition reveals stronger peak-directed interference. The structural separation and fresh-future advantage persist across four nominal depths at n=8-14, with 2.01-7.15 fold RP enrichment in the depth extensions at fixed, independently calibrated thresholds. Within the unconditioned ensemble, a structural prefix score predicts fresh-event probability without using the evaluated circuits' terminal outcomes. Population-preserving phase scrambling identifies a functional contribution from relative-phase organization across the tested settings, including primary-depth held-out confirmation. RP trajectory-guided initialization improves high-peak yield over Haar initialization under common local refinement. Intermediate multivariate guidance also improves the fresh-continuation susceptibility of constructed states beyond peak-only guidance across the same size-depth grid. Rare outputs thus reveal intermediate physical organization that remains useful under new dynamics and can guide circuit construction.

arXiv:2609.17482 [quant-ph]

(or arXiv:2609.17482v1 [quant-ph] for this version)

https://doi.org/10.48550/arXiv.2609.17482 Focus to learn more arXiv-issued DOI via DataCite (pending registration)

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