Methods, systems and apparatus for implementing a tunable qubit coupler. In one aspect, a device includes: a first data qubit, a second data qubit, and a third qubit that is a tunable qubit coupler arranged to couple to the first data qubit and to couple to the second data qubit such that, during operation of the device, the tunable qubit coupler allows tunable coupling between the first data qubit and the second data qubit.