Freiburg 2019 – wissenschaftliches Programm
FM 39.5: Talk
Dienstag, 24. September 2019, 15:15–15:30, 3044
cross-resonance-based gates between different superconducting quibt types — •xuexin xu1, mohammad ansari1, Jaseung ku2, yebin liu2, britton plourde2, jared hertzberg3, markus brink3, and jerry chow3 — 1Peter Grünberg Institute, Forschungszentrum Jülich — 2Syracuse University — 3IBM T.J. Waston Research Center
We theoretically model an experiment on a superconducting circuit made of a capacitively shunted flux qubit (CSFQ) and a Transmon qubit both capacitively coupled to a bus resonator in dispersive regime. To model this circuit we take into account the contribution of higher excited states in qubits and block-diagonalize the Hamiltonian perturbatively in the regime of small interaction couplings compared to frequency detuning. We apply external driving microwave pulses over all energy levels and consider the transitions they impose effectively within the computational subspace. More specifically we apply entirely microwave two-qubit gate, the so called cross-resonance, on CSFQ at sweet spot and away from it. Interestingly the two-qubit fidelity is largely enhanced at certain external flux away from the sweet spot. This enhancement takes place as the result of suppressed leakage out of computational subspace. This will introduce further tunability into two-qubit gate fidelity. Our theoretical results are in agreement with experiment, showing a promising approach to controllably improve single- and two-qubit gate operations in such circuits due to the relatively large and positive anharmonicity of CSFQ.