  Programmable optical tweezer arrays of molecules are an emerging platform for
quantum simulation and quantum information science. For these applications,
reducing and mitigating errors that arise during initial state preparation and
subsequent evolution remain major challenges. In this paper, we present work on
site-resolved detection of internal state errors and quantum erasures, which
are qubit errors with known locations. First, using a new site-resolved
detection scheme, we demonstrate robust and enhanced tweezer array preparation
fidelities. This enables creating molecular arrays with low defect rates,
opening the door to high-fidelity simulation of quantum many-body systems.
Second, for the first time in molecules, we demonstrate mid-circuit detection
of erasures using a composite detection scheme that minimally affects
error-free qubits. We also demonstrate mid-circuit conversion of
blackbody-induced errors into detectable erasures. Our demonstration of erasure
conversion, which has been shown to significantly reduce overheads for
fault-tolerant quantum error correction, could be useful for quantum
information processing in molecular tweezer arrays.
