A single antiproton, trapped and cooled to near absolute zero, behaves like a tuning fork that needs a very precise strike to produce a clean note. Catching that 'note' directly is nearly impossible — the signal is too weak. Physicists from the BASE collaboration came up with a clever trick: right next to the antiproton in the same trap sits a beryllium ion ion, which acts as a sensitive microphone. The antiproton and the ion are coupled by an electric field, like two balls connected by a spring: if one moves, the other immediately responds.
By measuring the beryllium ion's response, the scientists learn the state of the antiproton. This method allows measurement cycles to run hundreds of times faster than before and pushes precision toward the quantum limit — the boundary set by nature itself. The entire setup is a complex system of several traps cooled to cryogenic temperatures: at such cold, thermal noise nearly freezes, and the antiproton's weak signal can be discerned.
The goal is to test one of the strictest symmetries in physics, CPT symmetry. It states that if you replace a particle with its antiparticle, mirror space, and reverse time, the laws of nature remain unchanged. Any tiny violation of this symmetry would mean a crack in our understanding of the universe. So far, no crack has been found, but measurement precision keeps increasing, and each new digit after the decimal point is a step into the unknown.
The beryllium ion used as a 'microphone' is itself a quantum object: its state can be read out with a laser without destroying it.
In 'Star Trek', antimatter is used as fuel for warp drives, but no one there measures the antiproton's magnetic moment to twelve decimal places.