Characterization and Optimization of Tunable Couplers via Adiabatic Control in Superconducting Circuits

TL;DR

This paper presents a robust, hardware-efficient adiabatic control method for characterizing and tuning tunable couplers in superconducting quantum circuits, improving calibration and control precision without dedicated readout circuits.

Contribution

The authors develop a novel adiabatic swap technique for precise characterization and control of tunable couplers in superconducting circuits, enhancing scalability and calibration accuracy.

Findings

Achieved precise calibration of flux distortion in couplers.

Demonstrated control over dispersive shifts in qubit-resonator systems.

Expanded technique to tune qubit-resonator interactions over a wide range.

Abstract

In the pursuit of scalable superconducting quantum computing, tunable couplers have emerged as a pivotal component, offering the flexibility required for complex quantum operations of high performance. In most current architectures of superconducting quantum chips, such couplers are not equipped with dedicated readout circuits to reduce complexity in both design and operation. However, this strategy poses challenges in precise characterization, calibration, and control of the couplers. In this work, we develop a hardware-efficient and robust technique based on adiabatic control to address the above issue. The critical ingredient of this technique is adiabatic swap (aSWAP) operation between a tunable coupler and nearby qubits. Using this technique, we have characterized and calibrated tunable couplers in our chips and achieved straightforward and precise control over these couplers. For example, we have demonstrated the calibration and correction of the flux distortion of couplers. In addition, we have also expanded this technique to tune the dispersive shift between a frequency-fixed qubit and its readout resonator over a wide range.