Verifying the analogy between transversely coupled spin-1/2 systems and inductively-coupled fluxoniums

  1. Wei-Ju Lin,
  2. Hyunheung Cho,
  3. Yinqi Chen,
  4. Maxim G. Vavilov,
  5. Chen Wang,
  6. and Vladimir E. Manucharyan
We report a detailed characterization of two inductively coupled superconducting fluxonium qubits for implementing high-fidelity cross-resonance gates. Our circuit stands out because it behaves very closely to the case of two transversely coupled spin-1/2 systems. In particular, the generally unwanted static ZZ-term due to the non-computational transitions is nearly absent despite a strong qubit-qubit hybridization. Spectroscopy of the non-computational transitions reveals a spurious LC-mode arising from the combination of the coupling inductance and the capacitive links between the terminals of the two qubit circuits. Such a mode has a minor effect on our specific device, but it must be carefully considered for optimizing future designs.
arxiv pdf

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