  Enhancing the capabilities of superconducting quantum hardware, requires
higher gate fidelities and lower crosstalk, particularly in larger scale
devices, in which qubits are coupled to multiple neighbors. Progress towards
both of these objectives would highly benefit from the ability to fully control
all interactions between pairs of qubits. Here we propose a new coupler model
that allows to fully decouple dispersively detuned Transmon qubits from each
other, i.e. ZZ-crosstalk is completely suppressed while maintaining a maximal
localization of the qubits' computational basis states. We further reason that,
for a dispersively detuned Transmon system, this can only be the case if the
anharmonicity of the coupler is positive at the idling point. A simulation of a
40ns CZ-gate for a lumped element model suggests that achievable process
infidelity can be pushed below the limit imposed by state-of-the-art coherence
times of Transmon qubits. On the other hand, idle gates between qubits are no
longer limited by parasitic interactions. We show that our scheme can be
applied to large integrated qubit grids, where it allows to fully isolate a
pair of qubits, that undergoes a gate operation, from the rest of the chip
while simultaneously pushing the fidelity of gates to the limit set by the
coherence time of the individual qubits.
