Microwave activated two-qubit gate for fluxonium qubits via a tunable-transmon coupler

Abstract

Qubit lifetimes in superconducting transmon based quantum computers are a leading cause of gate infidelity. Furthermore, the transmon’s anharmonicity gives rise to frequency crowding on multi-qubit devices and limits the gate speed. The fluxonium qubit is a promising alternative to transmons, with coherence times reaching the order of milliseconds and anharmonicities on the order of gigahertz. In this work, we present a device containing two fluxonium qubits connected by a tunable-transmon coupler. By utilizing the higher levels of the fluxonium qubits and the transmon excited state, we explore the potential of a microwave activated CPHASE gate. We present results on a device designed to operate in a parameter space that has large qubit-to-qubit couplings and a reduced always-on ZZ interaction. This architecture is expected to facilitate faster, higher fidelity two-qubit gates. *This research was funded in part by the Office of the Director of National Intelligence (ODNI), Intelligence Advanced Research Projects Activity (IARPA), and by the Under Secretary of Defense for Research and Engineering under Air Force Contract No. FA8702-15-D-0001. L.D. acknowledges support from IBM through the IBM PhD Fellowship. The views and conclusions contained herein are those of the authors and should not be interpreted as necessarily representing the official policies or endorsements, either expressed or implied, of the ODNI, IARPA, the DoD, or the U.S. Government.