Two-Layer Verification for Fault-Tolerant Magic-State Preparation in High-Rate Quantum Codes

arXiv:2610.32267v1 Announce Type: new Abstract: Encoded magic states are essential for universal fault-tolerant quantum computation, but their resource-efficient preparation in high-rate quantum codes remains challenging. To address this limitation, we propose two-layer verification, which combines local verification of independently prepared subblocks with logical verification after their embedding into a target code. This hierarchy detects harmful error patterns, including even-parity logical-eigenvalue flips that are invisible to a collective product check alone. We demonstrate this scheme for a $[[21,3,5]]$ code by constructing a circuit that embeds three verified seven-qubit Steane-code magic states into the target code.