In situ tuning of coupled superconducting microwave resonators

Abstract

In order to transfer a range of important optical experiments into the microwave regime, a pair of near-identical, weakly coupled resonators is required. We describe a simple tuning mechanism for taking a pair of coupled, coplanar resonators through the avoided crossing in a controlled way. We see no obvious degradation of their high quality factor and find very good agreement with theoretical expectations.

Photon transfer in a system of coupled superconducting microwave resonators

“…A number of other techniques have been described in the literature, involving piezoelectric and ferroelectric layers, 31 magnetic field controlled SQUIDs, 32 voltage controlled paddles, 33 current controlled KI, 15 and simple mechanical tuning. 24 The first three compromise the Q and, in the case of SQUIDs or paddles, requires multiple patterning so, mechanical tuning would be the simplest method, although this would not lend itself to integration with more complex structures.…”

“…Lossless field tuning of single niobium CPRs with Q $ 10 6 has already been demonstrated, 14 albeit with rather small ($2 MHz) frequency modulation, and high Q's have also been shown in a pair of weakly coupled niobium CPRs. 24 Much larger (1-200 MHz) frequency changes with Q up to 2 Â 10 5 have been demonstrated in lumped element 25 and microstrip geometries for single NbTi resonators using current driven modulation. 15 This larger modulation is, in a)…”