Mode-selective coupling with low crosstalk between multi-mode coaxial transmons*

We present experimental results on statically coupled two-mode coaxial transmon qubits in which we utilise spatial symmetries to introduce highly mode-selective coupling. This allows for intrinsic crosstalk suppression between the protected modes that can be used for computation, whilst still allowing for fast entanglement operations, using the directly coupled ancillary modes. We demonstrate an all-microwave activated conditional phase gate, generating a fast entanglement operation between computational modes. We show this gate can be driven in multiple regimes and allows for a wide range of resonance conditions that can be met. Through simultaneous readout of both computational and ancillary modes, we show minimal leakage outside of the computational basis due to the entanglement operation.