qConnect: Increasing Qubit Connectivity in Quantum Computing Fabric Using Active Transmission Lines

Abstract

We present a novel approach for tunable superconductor microwave transmission lines and resonators that can be integrated on-chip using standard Al or Nb-based fabrication processes. By leveraging the nonlinear inductance of a Josephson junction, the impedance and, consequently, the resonance frequency of the lines can be adjusted via a small DC signal. This signal is inductively coupled to a superconducting quantum interference device loop, with the circuit designed to remain open at microwave frequencies, effectively preventing energy leakage. The simplicity and tunability of this design make it adaptable to various applications. In this work, we demonstrate the multiplexing capability of such design for use in dynamic connections between control circuits and qubits, as well as dynamic routing in quantum circuits.