Multi-Qubit coupler for superconducting circuits with controllable inductive interactions

Multi-qubit couplers are envisioned to provide fast gates between next-to-nearest neighbor qubits as well as between multiple qubits in one step. Common proposals, such as a capacitively coupled squid loop acting as a tunable element which however suffer from residual qubit-qubit interactions. Instead, this talk focuses on an architecture where all qubits connect inductively via squid loops to an intermediate node. In the limit of negligible capacitive coupling between the qubits and the coupler node, said intermediate node becomes frozen and enforces the appearance of interaction terms between all qubits connected to the coupler. We find a suitable configuration in parameter space, where by controlling the coupler with two external flux bias lines, pairwise interactions can be activated while other qubits remain decoupled. We present a derivation of the relevant circuit QED Hamiltonian and simulate parameter regimes that are experimentally accessible. We further explore its potential for creating multi-qubit gates.