What Would Settle the Leakage Attribution in Magic-State Cultivation on Willow

Abstract

Google's 2026 magic-state cultivation experiment on Willow grafts a cultivated magic state from a distance-3 color code into a distance-5 code that mixes color-code and surface-code stabilizers. In the supplement's memory experiment on that grafted code, the logical error rate is about seven times a depolarizing simulation that omits leakage. The authors call leakage the likely main cause, show two leakage signatures in the detector data, and ran no removal experiment. This note reads that attribution, records that the public data deposit holds no files for the nine-cycle run, and pre-registers a 2 by 2 removal and readout experiment. Until that experiment runs, the attribution stays likely and not ablated. The local distance-3 simulator is not a result of this note.