RFSQUID-Mediated Coherent Tunable Coupling Between a Superconducting Phase Qubit and a Lumped Element Resonator

TL;DR

This paper demonstrates a method for coherently and tunably coupling a superconducting phase qubit to a resonator using an RF SQUID, allowing dynamic control of their interaction strength.

Contribution

It introduces a flux-biased RF SQUID as a mediating element for tunable coupling, with experimental verification of coupling modulation from 0 to 100 MHz.

Findings

Coupling strength can be tuned via flux bias.

Spectroscopic splittings match theoretical models.

Vacuum Rabi oscillation frequency is modulated by flux bias.

Abstract

We demonstrate coherent tunable coupling between a superconducting phase qubit and a lumped element resonator. The coupling strength is mediated by a flux-biased RF SQUID operated in the non-hysteretic regime. By tuning the applied flux bias to the RF SQUID we change the effective mutual inductance, and thus the coupling energy, between the phase qubit and resonator . We verify the modulation of coupling strength from 0 to $100 MHz$ by observing modulation in the size of the splitting in the phase qubit's spectroscopy, as well as coherently by observing modulation in the vacuum Rabi oscillation frequency when on resonance. The measured spectroscopic splittings and vacuum Rabi oscillations agree well with theoretical predictions.