Overcoming barriers: Fast control of a qubit with variable protection

Fast, high fidelity control of protected superconducting qubits is fundamentally challenging due to their inherent insensitivity. To achieve high coherence and fast control simultaneously, we propose to use qubits with a variable level of T1-protection. In this way, fast gates can be performed using traditional microwave pulse techniques in the unprotected regime while the qubits enjoy extended relaxation times when idling in the protected regime. To test the performance of such a scheme, we propose a simple T1-protected qubit design, the double-shunted flux qubit (DSFQ), a variation of the capacitively shunted flux qubit, where the level of protection is controlled through a single tunable junction. We show numerically that the overhead due to tuning in and out of protection is minimal and that both single- and two-qubit gates can be performed with high fidelity without occupying the low coherence, non-computational states.