3D-wired coaxial circuit QED II: Evaluation of crosstalk

Evaluating crosstalk in multi-qubit superconducting circuits is becoming increasingly important. Control-wiring crosstalk can cause coherent control errors that become increasingly impractical to correct in larger scale circuits, and measurement crosstalk can induce dephasing. Selective control and coupling is intrinsic to our architecture [1] due to the use of coaxial circuit elements on two planes, mode-matched to out-of-plane 3D wiring. However, in any multi-qubit circuit the electromagnetic fields associated with individual circuit elements and control signals will never be perfectly confined. We present a careful characterisation of resonator and qubit control-line crosstalk, as well as measurement crosstalk due to coupling between neighboring qubits and resonators. We incorporate a detailed understanding of the two-qubit Hamiltonian in order to extract the qubit control-line crosstalk, and utilise measurement-induced dephasing to directly characterize resonator control-line, as well as measurement crosstalk.

[1] J. Rahamim et al., Appl. Phys. Lett. 110, 222602 (2017)