A Cooper-Pair Box Coupled to Two Resonators: An Architecture for a Quantum Refrigerator

TL;DR

This paper demonstrates a superconducting Cooper-pair box strongly coupled to two resonators, showing potential for use as a quantum refrigerator by integrating normal-metal resistors as heat baths.

Contribution

It reports the fabrication and spectroscopy of a charge qubit coupled to two resonators, and discusses modifications for quantum refrigeration applications.

Findings

Strong coupling between charge qubit and two resonators.

Voltage driving of the qubit at GHz frequencies achieved.

Proposed design for a cyclic quantum refrigerator.

Abstract

Superconducting circuits present a promising platform with which to realize a quantum refrigerator. Motivated by this, we fabricate and perform spectroscopy of a gated Cooper-pair box, capacitively coupled to two superconducting coplanar waveguide resonators with different frequencies. We experimentally demonstrate the strong coupling of a charge qubit to two superconducting resonators, with the ability to perform voltage driving of the qubit at GHz frequencies. We go on to discuss how the measured device could be modified to operate as a cyclic quantum refrigerator by terminating the resonators with normal-metal resistors acting as heat baths.