{"ID":23021115,"CreatedAt":"2026-09-17T04:55:43.771560302Z","UpdatedAt":"2026-09-17T04:55:43.771560302Z","DeletedAt":null,"paper_url":"https://arxiv.org/abs/2609.19116","arxiv_id":"2609.19116","title":"Comparing magic state cultivation methods using matrix product states","abstract":"Magic state cultivation prepares high-fidelity magic states at low expected space-time costs; however, the exact performance of some schemes is unsettled due to the difficulty in simulating non-Clifford circuits. Here, we use matrix-product states (MPS) based methods to compute the exact performance of two types of fold-transversal cultivation schemes: (i) the Sahay et al method based on the regular surface code S gate, and (ii) a method we propose based on a partially fault-tolerant fold-transversal S gate. We show that for the former protocol at $d=5$, the $|T\\rangle$ output reaches similar logical error rates to the $|S\\rangle$ output, traditionally used as a cheap full Clifford proxy. This contrasts with the $\\sim10\\times$ discrepancy reported for the $d=5$ colour-code scheme of Gidney et al. We also find that our new $d=5$ scheme has $\\sim1.3\\times$ lower expected space-time cost while still reaching $10^{-9}$ logical error rate. We show that MPS and Clifford-augmented MPS (CAMPS) perform on par with or even better than the recently introduced near-Clifford simulator Clifft on the hardest $d=5$ regular surface code scheme. Additionally, to speed up simulation, we propose a new pre-screening method based on simple Pauli propagation, lowering by up to three orders of magnitude the required number of exact simulations, and use several simulator-agnostic sampling methods such as subset sampling.","short_abstract":"Magic state cultivation prepares high-fidelity magic states at low expected space-time costs; however, the exact performance of some schemes is unsettled due to the difficulty in simulating non-Clifford circuits. Here, we use matrix-product states (MPS) based methods to compute the exact performance of two types of fol...","url_abs":"https://arxiv.org/abs/2609.19116","url_pdf":"https://arxiv.org/pdf/2609.19116v1","authors":"[\"Tom Hartweg\",\"Asier Piñeiro Orioli\"]","published":"2026-09-16T17:41:54Z","proceeding":"quant-ph","tasks":"[\"quant-ph\"]","methods":"[]","has_code":false}