An apparatus includes: a transmission line resonator; and multiple resonators coupled to the transmission line resonator, in which each resonator of the multiple resonators is coupled to the transmission line resonator at a different position X along a length of the transmission line resonator, and in which, for each resonator of the multiple resonators, a coupling position Y along a length of the resonator is selected such that, upon application of a source potential to the resonator, a standing wave established in the resonator is impedance and phase matched to a standing wave established in the transmission line resonator.