Cayley Commutator-free Methods for Krotov-Type Algorithms in Quantum Optimal Control

Fuente: arXiv
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Main Authors: Wembe, Boris, Ali, Usman, Meier, Torsten, Ober-Blöbaum, Sina
Format: Preprint
Published: 2026
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author Wembe, Boris
Ali, Usman
Meier, Torsten
Ober-Blöbaum, Sina
author_facet Wembe, Boris
Ali, Usman
Meier, Torsten
Ober-Blöbaum, Sina
contents This paper presents a class of structure-preserving numerical methods for quantum optimal control problems, based on commutator-free Cayley integrators. Starting from the Krotov framework, we reformulate the forward and backward propagation steps using Cayley-type schemes that preserve unitarity and symmetry at the discrete level. This approach eliminates the need for matrix exponentials and commutators, leading to significant computational savings while maintaining higher-order accuracy. We first recall the standard linear setting and then extend the formulation to nonlinear Schrödinger and Gross-Pitaevskii equations using a Cayley-polynomial interpolation strategy. Numerical experiments on state-transfer problems illustrate that the CF-Cayley method achieves the same accuracy as high-order exponential or Cayley-Magnus schemes at substantially lower cost, especially for longtime or highly oscillatory dynamics. In the nonlinear regime, the structure-preserving properties of the method ensure stability and norm conservation, making it a robust tool for large-scale quantum control simulations. The proposed framework thus bridges geometric integration and optimal control, offering an efficient and reliable alternative to existing exponential-based propagators.
format Preprint
id arxiv_https___arxiv_org_abs_2603_11697
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Cayley Commutator-free Methods for Krotov-Type Algorithms in Quantum Optimal Control
Wembe, Boris
Ali, Usman
Meier, Torsten
Ober-Blöbaum, Sina
Numerical Analysis
Optimization and Control
This paper presents a class of structure-preserving numerical methods for quantum optimal control problems, based on commutator-free Cayley integrators. Starting from the Krotov framework, we reformulate the forward and backward propagation steps using Cayley-type schemes that preserve unitarity and symmetry at the discrete level. This approach eliminates the need for matrix exponentials and commutators, leading to significant computational savings while maintaining higher-order accuracy. We first recall the standard linear setting and then extend the formulation to nonlinear Schrödinger and Gross-Pitaevskii equations using a Cayley-polynomial interpolation strategy. Numerical experiments on state-transfer problems illustrate that the CF-Cayley method achieves the same accuracy as high-order exponential or Cayley-Magnus schemes at substantially lower cost, especially for longtime or highly oscillatory dynamics. In the nonlinear regime, the structure-preserving properties of the method ensure stability and norm conservation, making it a robust tool for large-scale quantum control simulations. The proposed framework thus bridges geometric integration and optimal control, offering an efficient and reliable alternative to existing exponential-based propagators.
title Cayley Commutator-free Methods for Krotov-Type Algorithms in Quantum Optimal Control
topic Numerical Analysis
Optimization and Control
url https://arxiv.org/abs/2603.11697