# Krotov: A Python implementation of Krotov's method for quantum optimal control

## TL;DR

The paper introduces 'krotov', an open-source Python package that implements Krotov's quantum optimal control method, enabling efficient design of control fields for various quantum tasks with guaranteed convergence.

## Contribution

It provides a user-friendly, customizable Python tool for quantum optimal control based on Krotov's method, expanding accessible solutions for quantum system optimization.

## Key findings

- Guarantees monotonic convergence for control fields.
- Supports diverse quantum control problems like state transfer and gate implementation.
- Eases integration with other Python tools for quantum computing.

## Abstract

We present a new open-source Python package, krotov, implementing the quantum optimal control method of that name. It allows to determine time-dependent external fields for a wide range of quantum control problems, including state-to-state transfer, quantum gate implementation and optimization towards an arbitrary perfect entangler. Krotov's method compares to other gradient-based optimization methods such as gradient-ascent and guarantees monotonic convergence for approximately time-continuous control fields. The user-friendly interface allows for combination with other Python packages, and thus high-level customization. The package is being developed at https://github.com/qucontrol/krotov