[cancelled] Implementation of a high-fidelity Walsh-Hadamard gate with superconducting qutrits - Adrian Lupascu

We have implemented a Walsh-Hadamard gate, which realizes the quantum Fourier transform, in a superconducting qutrit. The qutrit is encoded in the lowest three energy levels of a capacitively shunted flux device. The device design combines high anharmonicity and long coherence times.\r\nThe Walsh-Hadamard gate is implemented in an optimized way, combining two unitaries, generated by off-diagonal and diagonal Hamiltonians respectively. The gate implementation utilizes simultaneous driving of all three transitions between the three pairs of energy levels of the qutrit, one of which is implemented with a two-photon process. The gate has a duration of 35 ns and an average fidelity of 99.2%, characterized with quantum state tomography. Compensation of ac-Stark and Bloch-Siegert shifts is essential for reaching high gate fidelities.\r\nWe discuss future prospects for qutrits and higher dimensionality qudits implemented with superconducting devices.