Systems, devices, and methods for controllably coupling qubits

A superconducting coupler comprising:

• a first superconducting loop that is interrupted by a split junction, the split junction comprising a second superconducting loop that is interrupted by at least two Josephson junctions, wherein the at least two Josephson junctions are electrically connected in parallel with one another with respect to the first superconducting loop;
• and
• means for tuning a Josephson energy of the split junction, wherein the Josephson energy of the split junction determines a coupling state of the first superconducting loop, the coupling state being selected from the group consisting of ferromagnetic coupling, anti-ferromagnetic coupling, and zero coupling, and wherein the first superconducting loop is positioned to communicably couple to both a first superconducting qubit and a second superconducting qubit.

A method of coupling two superconducting qubits through a superconducting coupler comprising a first superconducting loop that is interrupted by a split junction and means for tuning a magnetic flux in the split junction, wherein the first superconducting loop is positioned to communicably couple to both a first superconducting qubit and a second superconducting qubit, the method comprising:

• tuning the magnetic flux in the split junction to provide at least one of zero coupling, ferromagnetic coupling, and anti-ferromagnetic coupling between the first superconducting qubit and the second superconducting qubit.