Suppress parasitic capacitances in soft 0-$\pi$ coupling architectures

Suppress parasitic capacitances in the multi-node capacitive coupling networks required to implement two-qubit gates between soft 0-$\pi$ qubits, thereby enabling experimentally practical circuit layouts and reducing unwanted residual interactions.

Background

The proposed two-qubit coupling schemes require capacitive access to all four nodes of each soft 0-$\pi$ qubit, together with a multi-node coupling network and additional drive and readout circuitry. This makes the layouts substantially more complex than those used for conventional superconducting qubits.

The analysis assumes identical circuit elements and therefore exact cancellation of unwanted coupling terms. In realistic devices, disorder in coupling capacitors and stray capacitances can break this symmetry and generate residual interactions, making suppression of parasitic capacitances an experimentally significant unresolved challenge.