NQCP Life in Quantum - Postdoc Frederik Nathan, Niels Bohr Institute

Self-correcting GKP qubit and gates in a driven-dissipative circuit

We propose a protocol and circuit-QED architecture for creating and dissipatively error-correcting GKP qubits. The device consists of a high-impedance LC resonator coupled to a large Josephson junction and a resistor through a time-dependent switch. Controlling the switch via a  particular family of stepwise  protocols drives the system into a regime of dissipative error correction, where the resistor ats to correct both phase and amplitude errors. We show in simulations that the onset of dissipative error correction leads to exponential life-time enhancement, reaching macroscopic (+10 ms) scales for near-feasible parameters, even in the presence of external noise. The qubit supports self-correcting Clifford gates, where control noise is dissipatively corrected, leading to exponentially-scaling gate fidelity. The qubit can be directly read out and initialized via measurement of the supercurrent in the Josephson junction.                   

Collaboration between NBI, Caltech, and AWS.