Fast feedback for active noise cancellation in superconducting qubits*

Superconducting qubits are a promizing platform for realizing quantum computer. However, due to recent advances in qubit control, both single- and two-qubit gate fidelities are starting to be limited by the coherence times of the qubits. Here we show that by employing fast-feedback to cancel low-frequency noise disturbing the circuit, the fluctuations in the qubit frequency are stabilized, resulting in improved coherence time and gate fidelities. This enables high-fidelity operation of transmon qubits even when they are biased away from their flux sweetspot, helping to solve frequency crowding issues as well as reducing drifts in control parameters.