In a major milestone for quantum physics and antimatter research, we at BASE have demonstrated the first coherent spectroscopy with a single antiproton spin. By keeping a single antiproton oscillating coherently between the "spin-up" and the "spin-down" states for 50 seconds, we've demonstrated quantum control over a fundamental antimatter particle — something never done before.

This breakthrough, published today in Nature, was made possible by a major upgrade to our Penning trap experiment at CERN's Antimatter Factory. We suppressed the decoherence mechanisms that previously limited precision, allowing us to perform the coherent spin spectroscopy on an individual antiproton.

This work not only establishes a new benchmark for spin coherence in antimatter systems but also opens the door to ultra-precise tests of matter-antimatter symmetry. It sets the stage for future measurements with 10–100× improved precision, and strongly motivates transporting of antiprotons to calmer magnetic environments at HHU using our transportable antiproton trap BASE-STEP.

We're excited to share this step towards better constraining the standard model of particle physics.

https://www.nature.com/articles/s41586-025-09323-1