Mitigating information leakage in a crowded spectrum of weakly anharmonic qubits

摘要

A challenge for scaling up quantum processors using frequency-crowded, weaklyanharmonic qubits is to drive individual qubits without causing leakage intonon-computational levels of the others, while also minimizing the number ofcontrol lines. To address this, we implement single-qubit Wah-Wah control in acircuit QED processor with a single feedline for all transmon qubits, operatingat the maximum gate speed achievable given the frequency crowding. Randomizedbenchmarking and quantum process tomography confirm alternating qubit controlwith $\leq$1% average error per computational step and decoherence-limitedidling of one qubit while driving another with a Wah-Wah pulse train.