SYSTEMS, DEVICES, AND METHODS FOR CONTROLLABLY COUPLING QUBITS

A system for communicably coupling between two superconducting qubits may include an rf-SQUID coupler having a loop of superconducting material interrupted by a compound Josephson junction and a first magnetic flux inductor configured to controllably couple to the compound Josephson junction. The loop of superconducting material may be positioned with respect to a first qubit and a second qubit to provide respective mutual inductance coupling therebetween. The coupling system may be configured to provide ferromagnetic coupling, anti-ferromagnetic coupling, and/or zero coupling between the first and second qubits. The rf-SQUID coupler may be configured such that there is about zero persistent current circulating in the loop of superconducting material during operation.