Title: Tunable Superconducting Qubits with Flux-Independent Coherence,
Abstract: We have studied the impact of low-frequency magnetic flux noise upon
superconducting transmon qubits with various levels of tunability. We find that
qubits with weaker tunability exhibit dephasing that is less sensitive to flux
noise. This insight was used to fabricate qubits where dephasing due to flux
noise was suppressed below other dephasing sources, leading to flux-independent
dephasing times T2* ~ 15 us over a tunable range of ~340 MHz. Such tunable
qubits have the potential to create high-fidelity, fault-tolerant qubit gates
and fundamentally improve scalability for a quantum processor.