Scalable coherent manipulation of qubit quantum states is crucial for building large-scale superconducting quantum processors towards fault-tolerant quantum computing. Complete coherent manipulation contains quantum gate control and magnetic flux bias for the qubit, especially for quantum processors with frequency-tunable qubits and tunable couplers. In recent years, efforts have been made to propose quantum gate control in a scalable way. However, proposals and experiments for scalable magnetic flux bias for qubits are rarely reported. Here, we propose a scalable scheme to provide magnetic flux for qubits by using an on-chip direct current source (OCDCS). We demonstrate both theoretically and experimentally that only single pulse is needed to deterministically modulate the magnetic flux in the OCDCS, which then provides the qubit with in situ and constant magnetic flux. With the magnetic flux provided by the OCDCS, the experimental results exhibit high-fidelity single-qubit gate and low noise current of the OCDCS, which shows a 15.6 dB reduction compared with that of the RTE scheme. Additionally, we propose a time-division-multiplex (TDM) scheme combining the OCDCS with switch arrays, which could exponentially reduce the number of cables for flux bias from traditional $n$ to ${\log }_2(n)+1$. Our work thus paves the way for scalable flux bias in large-scale superconducting quantum processors.

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• Optoelectronics
• Quantum computation
• Quantum control
• Quantum information with solid state qubits
• Radio frequency power sources
• Multiplexers
• SQUID
• Superconducting qubits