In a groundbreaking development for antimatter research, the BASE collaboration at CERN has successfully kept a single antiproton— the antimatter counterpart of a proton—oscillating smoothly between two quantum states for nearly a minute while trapped. This milestone, detailed in a recent Nature publication, marks the first demonstration of an antimatter quantum bit, or qubit, paving the way for far more precise comparisons between matter and antimatter behavior.
Antiprotons, like protons, possess a quantum property called spin, which behaves like a tiny magnetic moment pointing either “up” or “down.” By measuring transitions between these spin states using coherent quantum transition spectroscopy, scientists gain a powerful tool for quantum sensing and precision tests of fundamental physics, such as charge-parity-time (CPT) symmetry. This symmetry posits that matter and antimatter should behave identically, yet our Universe’s matter dominance challenges this idea.
Until now, coherent quantum transitions had been observed in large particle groups or trapped ions but never in a single free nuclear magnetic moment like an antiproton’s spin. Using a sophisticated array of electromagnetic Penning traps at CERN’s antimatter factory, the BASE team managed to control the antiproton’s spin states with remarkable precision. The analogy often used is like pushing a playground swing—giving the right timed “push” to sustain a smooth oscillation between spin-up and spin-down states.
Previous measurements of the antiproton’s magnetic moment achieved incredible precision but relied on incoherent spectroscopy, which suffered from magnetic noise and measurement interference. The latest advance suppresses these issues, allowing coherent spectroscopy with a spin coherence time of 50 seconds—long enough to perform detailed studies.
This breakthrough, the first antimatter qubit, opens new opportunities for precision antimatter experiments with potentially 10 to 100 times improved accuracy. While immediate applications outside fundamental physics are unlikely, future upgrades, such as the BASE-STEP project, aim to extend coherence times even further by transporting antiprotons to quieter magnetic environments. This promises to revolutionize antimatter research and deepen our understanding of the Universe’s fundamental symmetries.
