Cancelling microwave crosstalk with fixed-frequency qubits

TL;DR

This paper introduces a calibration method using the AC Stark effect to cancel microwave crosstalk in fixed-frequency superconducting qubits, improving the fidelity of parallel quantum gate operations.

Contribution

It presents a novel calibration technique based on interference patterns to effectively reduce microwave crosstalk in fixed-frequency qubit arrays.

Findings

Significant reduction of crosstalk errors in a 7-qubit array

Reliable identification of optimal compensation parameters

Enhanced parallel gate operation fidelity

Abstract

Scalable quantum information processing requires that modular gate operations can be executed in parallel. The presence of crosstalk decreases the individual addressability, causing erroneous results during simultaneous operations. For superconducting qubits which operate in the microwave regime, electromagnetic isolation is often limited due to design constraints, leading to signal crosstalk that can deteriorate the quality of simultaneous gate operations. Here, we propose and demonstrate a method based on AC Stark effect for calibrating the microwave signal crosstalk. The method is suitable for processors based on fixed-frequency qubits which are known for high coherence and simple control. The optimal compensation parameters can be reliably identified from a well-defined interference pattern. We implement the method on an array of 7 superconducting qubits, and show its effectiveness in removing the majority of crosstalk errors.