Implementing leakage reduction units for quantum error correction with superconducting qubits*

Leakage presents a major threat to quantum error correction with superconducting qubits. We present the realization of hardware-efficient leakage reduction units (LRU) in superconducting qubits in the context of quantum error correction. In particular, we show LRUs suitable for both ancilla and data qubits and benchmark their performance in the leakage and qubit subspaces. Finally, we assess the impact of the LRU operations on repeated stabilizer measurements in a 17-transmon device designed for the distance-3 surface code.