Seminar - Ass. Professor Christian Andersen, TU Delft

Fluxonium qubits – readout and gates

Superconducting qubits have enabled recent progress in experiments with large quantum computing circuits. In these, transmon has been the broadly used qubit of choice. To further improve the performance of such circuits, the introduction of the fluxonium qubit can bring added benefits of longer coherence times and larger anharmonicity. In this talk, I will briefly discuss how we can perform fast readout of fluxonium qubits using a flux-pulse assisted readout. Increasing the dispersive shift magnitude by almost 20\% through flux pulsing, we achieve an assignment fidelity of 94.3% with an integration time of 280 ns which is significantly faster than previous fluxonium readout schemes. Next, I will discuss how we can overcome single-qubit errors in fluxonium qubit due to the breakdown of the rotating wave approximation. Finally, I'll discuss two-qubit gates with fluxonium qubits. In our experiment we observe low leakage, fast two qubit gates (< 50ns) and high two-qubit gate fidelities (~99%). We demonstrate experimentally that different pulse schemes can speed up the duration of the gate.