boundary. In electromagnetic finite-element simulators such ports will typically be defined as wave ports on the planes (perpendicular to the direction of propagation) in the cross-sections of the drive lines. Such a choice for the drive ports will include any crosstalk happening in the transition region (such as a spurious chip boundary mode [@Wirebond-Crosstalk-Martinis] for example) in our crosstalk measures defined above. See Appendix for more details on how to define the drive ports in electromagnetic finite-element simulators.

Example: Classical crosstalk in a multi-qubit device
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![\[fig:2x8-device-model-with-drives\]Top: Augmented 2x8 device model with readout resonators and drive ports added. Readout resonators are represented with edges linking qubits $Q_{k}$’s to their drive ports $P_{k}$’s. Bottom: How much of the drive voltage leaks into other qubits in the upper row in the 2x8 multi-qubit device on the top figure above when only the qubit $Q_{1}$ is excited through its drive port $P_{1}$: classical crosstalk decays exponentially as a function of distance from the qubit $Q_{1}$ to the right in the first row of the circuit in the figure on the top. ](figs/2by8_2QbyBUS_with_drives "fig:")\
![\[fig:2x8-device-model-with-drives\]Top: Augmented 2x8 device model with readout resonators and drive ports added. Readout resonators are represented with edges linking qubits 