# Optimised surface-electrode ion-trap junctions for experiments with cold molecular ions

## TL;DR

This paper presents the design and optimization of surface-electrode ion-trap junctions for experiments with cold molecular ions, enabling advanced chip-based trapping techniques for various scientific applications.

## Contribution

It introduces a multi-objective optimization procedure for planar ion-trap junctions and proposes a multi-functional chip for cold molecular ion experiments.

## Key findings

- Optimized junction designs for quadrupole and octupole configurations.
- Proposed a multi-functional ion-trap chip for millikelvin temperature molecular ions.
- Opened pathways for complex chip-based trapping in quantum technology and chemistry.

## Abstract

We discuss the design and optimisation of two types of junctions between surface-electrode radiofrequency ion-trap arrays that enable the integration of experiments with sympathetically cooled molecular ions on a monolithic chip device. A detailed description of a multi-objective optimisation procedure applicable to an arbitrary planar junction is presented, and the results for a cross junction between four quadrupoles as well as a quadrupole-to-octupole junction are discussed. Based on these optimised functional elements, we propose a multi-functional ion-trap chip for experiments with translationally cold molecular ions at temperatures in the millikelvin range. This study opens the door to extending complex chip-based trapping techniques to Coulomb-crystallised molecular ions with potential applications in mass spectrometry, spectroscopy, controlled chemistry and quantum technology.