QDev Seminar: Liam O’Brien, Caltech

Self-correcting qubits and universal single-qubit computation in a driven-dissipative circuit

We propose a circuit architecture for a dissipatively error-corrected GKP qubit. The device consists of a high-impedance LC circuit coupled to a Josephson junction and a resistor via a controllable switch. When the switch is activated via a particular family of stepwise protocols, the resistor absorbs all noise-induced entropy, resulting in dissipative error correction of both phase and amplitude errors. This leads to an exponential increase of qubit lifetime, reaching beyond the millisecond scale in simulations with near-feasible parameters. We show the qubit supports native self-correcting Clifford gates, and we also outline schemes for performing fast (microsecond-scale) non-Clifford gates. In all cases, dissipative error-correction of control noise leads to an exponential suppression of gate infidelity. We finally show how the qubit can be read out and initialized via measurement of the supercurrent in the Josephson junction, meaning this architecture provides a platform for self-correcting, universal single-qubit quantum computation.