Towards a fluxonium-based quantum processor II: interacting qubits

We describe our progress in experimentally realizing a microwave-activated two-qubit gate with capacitively coupled fluxonium qubits. When biased at the flux sweet-spot, the individual qubits have frequencies around 500 MHz and reproducibly reach long coherence times in excess of 100 us (the best device had T₂ > 300 us) [1]. A c-Phase gate can be achieved by sending a short 2π-pulse at the frequency near the 1→2 transition of the target qubit [2]. Our work includes characterization of coherence and parameter fluctuations in multi-qubit chips, modeling and experimentally validating the two-qubit interactions, optimizing the joint readout, and benchmarking of the gate operations.

[1] Nguyen et al., arXiv preprint arXiv:1810.11006v1 (2018)
[2] Nesterov et al., Phys. Rev. A 98, 030301 (2018)