Automation in quantum logic experiments with cold molecular ions

TL;DR

This paper introduces a fully automated control system for cold molecular ion experiments, significantly increasing efficiency and enabling robust, unsupervised quantum logic measurements with scalable design.

Contribution

The authors develop a modular, automated control system that enhances experimental throughput and robustness in cold molecular ion quantum logic experiments.

Findings

Increased experimental cycles by about ten times compared to manual operation.

Achieved about eight times more loaded molecules in practical situations.

Enabled long-term, unsupervised quantum-logic spectroscopy with real-time data analysis.

Abstract

Modern experiments with cold molecular ions have reached a high degree of complexity requiring frequent sample preparation, state initialization and protocol execution while demanding precise control over multiple devices and laser sources. To maintain a high experimental duty cycle and robust measurement conditions, automation becomes essential. We present a fully automated control system for the preparation of trapped state-selected molecular ions and subsequent quantum logic-based experiments. Adaptive feedback routines based on real-time image analysis introduce and identify single molecular ions in atomic-ion Coulomb crystals. By appropriate manipulation of the trapping potentials, excess atomic ions are released from the trap to produce dual-species two-ion strings, here Ca$^+-$N$_2^+$. After mass and state identification of the molecular ion, nanosecond-level synchronization of laser pulses employing the Sinara/ARTIQ framework and real-time data analysis enable quantum-logic-spectroscopic measurements. The present automated control system enables robust, unsupervised operation over extended periods resulting in an increase of the number of experimentation cycles by about a factor of ten compared to manual operation and a factor of about eight in loaded molecules in typical practical situations. The modular, distributed design of the system provides a scalable blueprint for similar molecular-ion experiments.