Strong tunable coupling between a superconducting charge and phase qubit

TL;DR

This paper demonstrates a tunable coupling mechanism between a charge qubit and a phase qubit, allowing independent control and entanglement, with measurements aligning with theoretical predictions.

Contribution

It introduces a circuit enabling large-range tunable coupling between superconducting qubits with independent manipulation and entanglement capabilities.

Findings

Measured coupling strength matches analytic theory.

Achieved independent manipulation of each qubit.

Demonstrated entanglement between charge and phase qubits.

Abstract

We have realized a tunable coupling over a large frequency range between an asymmetric Cooper pair transistor (charge qubit) and a dc SQUID (phase qubit). Our circuit enables the independent manipulation of the quantum states of each qubit as well as their entanglement. The measurements of the charge qubit's quantum states is performed by resonant read-out via the measurement of the quantum states of the SQUID. The measured coupling strength is in agreement with an analytic theory including a capacitive and a tunable Josephson coupling between the two qubits.