Advanced quantum-logic control for molecular ions

• Applicant: Dr. Fabian Wolf
• Subject Area: Optics, Quantum Optics and Physics of Atoms, Molecules and Plasmas
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 550848493

In this project we aim to develop advanced molecular quantum control techniques in a new collaboration consisting of three research groups at ETH Zürich (ETH), Physikalisch-Technische Bundesanstalt Braunschweig (PTB), and the University of Innsbruck (UIBK). Precise quantum control over all degrees of freedom of individual molecules represents a challenging and cutting-edge frontier which will push the boundaries of quantum technologies and will enable the study of molecules with unparalleled measurement precision. Achieving such control will directly enable precision tests of fundamental theories, significantly influence the search for new physics, and allow the development of new quantum information processing paradigms. Quantum control of single molecular ions has recently been achieved, in part by pioneering work from the consortium groups. Our objective is to extend and improve this tool-set. This includes its extension to additional molecular species, higher rotational states and multiple molecular ions. Thereby we approach our long-term goals of the individual groups which are (i) high precision spectroscopy of the hydrogen molecular ion (ETH), (ii) test of symmetry violation using entangled diatomic polar molecules (PTB), (iii) demonstration of the primitives for quantum information science with molecular ions (UIBK). The extensive range of expertise needed to achieve these long-term objectives, spanning from molecular physics and precision measurements to quantum information processing, makes these endeavors especially demanding. Within this collaborative effort, this challenge is addressed by leveraging the complementary expertise of the research groups and making use of three different molecular ion experiment setups to fast-track the development and provide widely applicable tools. The different molecular ions utilized by the research groups (H2+, MgH+, CaH+, CaOH+) have complementary properties. This enables us (i) to develop new techniques initially on the most suitable system, subsequently adapting the techniques to the other species, (ii) pursue complementary techniques in a comparative approach. Developing these techniques will enable us to implement the following primary goals within this proposal: (i) Deterministic pure quantum state preparation of a non-polar molecule relying only on quantum logic spectroscopy techniques; (ii) rotational quantum logic spectroscopy of the hydrogen molecular ion; (iii) preparation of an entangled, decoherence-free subspace state of two molecular ions; (iv) implementing quantum error correction on a molecular ion. These achievements will all extend the state-of-the-art considerably, as none of these have been achieved so far. They present major milestones towards the groups' long-term goals and would be generally applicable to quantum control of molecular ions, contributing new tools to this high-impact research field.

• DFG Programme: Research Grants
• International Connection: Austria, Switzerland
• Partner Organisation: Fonds zur Förderung der wissenschaftlichen Forschung (FWF)
• Cooperation Partners: Dr. Daniel Kienzler; Professor Philipp Schindler, Ph.D.