# Composite pulses with errant phases

## TL;DR

This paper introduces novel composite pulse sequences that not only correct common experimental errors in quantum control but also compensate for systematic phase errors, enhancing robustness and fidelity in quantum operations.

## Contribution

It presents two new types of composite pulse sequences that specifically address and correct systematic phase errors, a challenge in precise quantum control.

## Key findings

- Sequences tolerate up to 10% phase errors for high fidelity
- Sequences maintain over 99.99% fidelity under certain error conditions
- Enhanced robustness against pulse area and detuning errors

## Abstract

Composite pulses --- sequences of pulses with well defined relative phases --- are an efficient, robust and flexible technique for coherent control of quantum systems. Composite sequences can compensate a variety of experimental errors in the driving field (e.g. in the pulse amplitude, duration, detuning, chirp, etc.) or in the quantum system and its environment (e.g. inhomogeneous broadening, stray electric or magnetic fields, unwanted couplings, etc.). The control parameters are the relative phases between the constituent pulses in the composite sequence, an accurate control over which is required in all composite sequences reported hitherto. In this paper, we introduce two types of composite pulse sequences which, in addition to error compensation in the basic experimental parameters, compensate systematic errors in the composite phases. In the first type of such composite sequences, which compensate pulse area errors, relative phase errors of up to 10% can be tolerated with reasonably short sequences while maintaining the fidelity above the 99.99% quantum computing benchmark. In the second type of composite sequences, which compensate pulse area and detuning errors, relative phase errors of up to 5% can be compensated.