Frequency Up-Conversion Schemes for Controlling Superconducting Qubits

TL;DR

This paper compares traditional IQ mixing and a novel double frequency conversion method for generating microwave pulses to control superconducting qubits, demonstrating improved spurious-free range and comparable performance.

Contribution

It introduces and experimentally evaluates a double frequency conversion scheme that eliminates the need for IQ calibration in superconducting qubit control.

Findings

Double frequency conversion achieves over 70 dB spurious-free dynamic range.

The new method matches IQ mixing in qubit control fidelity.

The approach simplifies pulse generation by removing calibration requirements.

Abstract

High-fidelity control of superconducting qubits requires the generation of microwave-frequency pulses precisely tailored on nanosecond timescales. These pulses are most commonly synthesized by up-converting and superimposing two narrow-band intermediate-frequency signals referred to as the in-phase (I) and quadrature (Q) components. While the calibration of their DC-offsets, relative amplitude and phase allows one to cancel unwanted sideband and carrier leakage, this IQ mixing approach suffers from the presence of additional spurious frequency components. Here, we experimentally study an alternative approach based on double frequency conversion, which overcomes this challenge and circumvents the need for IQ-calibration. We find a spurious-free dynamic range of more than 70$\,$dB and compare the quality of pulse generation against a state-of-the-art IQ mixing scheme by performing repeated single-qubit randomized benchmarking on a superconducting qubit.