Road transport of trapped antiprotons

Low-energy antiprotons confined in ultrahigh-vacuum Penning traps¹ enable precision investigations of charge, parity and time-reversal (CPT) invariance² to test the fundamental symmetry between matter and antimatter. These studies are driven by the search for physics beyond the standard model of particle physics, including efforts to explain the observed cosmological matter-antimatter asymmetry. Until now, such experiments have only been possible at CERN's Antimatter Factory^3,4. At present, magnetic-field fluctuations caused by the facility operation limit the sensitivity of trapped-antiproton precision measurements⁵, which provide the most stringent matter-antimatter symmetry tests in the baryon sector^6-9. This has inspired us to develop the cryogenic, open and transportable Penning-trap system BASE-STEP^5,10, designed to relocate antiprotons into low-noise offline laboratories, a strategy expected to enable at least 100-fold improved CPT tests^9,11. Here we demonstrate the road transport of antiprotons trapped in BASE-STEP. Ninety-two trapped antiprotons have been transported outside the Antimatter Factory along a 7.5-km route without particle loss or measurable degradation of the trap vacuum. This achievement marks the starting point for a new era of antiproton precision measurements^8,12 in dedicated low-noise offline laboratory environments.