Sympathetic cooling of positrons to cryogenic temperatures for antihydrogen production

The positron, the antiparticle of the electron, predicted by Dirac in 1931 and discovered by Anderson in 1933, plays a key role in many scientific and everyday endeavours. Notably, the positron is a constituent of antihydrogen, the only long-lived neutral antimatter bound state that can currently be synthesized at low energy, presenting a prominent system for testing fundamental symmetries with high precision. Here, we report on the use of laser cooled Be+ ions to sympathetically cool a large and dense plasma of positrons to directly measured temperatures below 7 K in a Penning trap for antihydrogen synthesis. This will likely herald a significant increase in the amount of antihydrogen available for experimentation, thus facilitating further improvements in studies of fundamental symmetries.

Sympathetic cooling of a trapped proton mediated by an LC circuit

Efficient cooling of trapped charged particles is essential to many fundamental physics experiments1,2, to high-precision metrology3,4 and to quantum technology5,6. Until now, sympathetic cooling has required close-range Coulomb interactions7,8, but there has been a sustained desire to bring laser-cooling techniques to particles in macroscopically separated traps5,9,10, extending quantum control techniques to previously inaccessible particles such as highly charged ions, molecular ions and antimatter. Here we demonstrate sympathetic cooling of a single proton using laser-cooled Be+ ions in spatially separated Penning traps. The traps are connected by a superconducting LC circuit that enables energy exchange over a distance of 9 cm. We also demonstrate the cooling of a resonant mode of a macroscopic LC circuit with laser-cooled ions and sympathetic cooling of an individually trapped proton, reaching temperatures far below the environmental temperature. Notably, as this technique uses only image–current interactions, it can be easily applied to an experiment with antiprotons1, facilitating improved precision in matter–antimatter comparisons11 and dark matter searches12,13.

Tuning of relative spatial distributions of a two-component ion system to improve sympathetic cooling efficiency

Herein, a fine-tuning method is proposed for the spatial distributions of a mixed three-dimensional (3D) ion system in dual radio frequency (RF) linear Paul traps to achieve efficient sympathetic cooling. The dual RF field matching, efficient capture method and transient process of the intrinsic micromotion of the mixed ion system are analyzed quantitatively by numerical simulations. The 3D correlation coupling characteristics between intrinsic micromotion and secular motion of ion system are obtained. It is found that reasonable low-frequency trapping potential can produce ultra-low-frequency pulling effect on ions with low mass-to-charge ratio (M/Q), which is beneficial to the dynamic coupling between ions with large M/Q differences. The effects of equivalent stiffness coefficients [Formula: see text] on the relative spatial configuration and dynamic coupling process of mixed 3D ion crystals with large M/Q differences are discussed. By tuning [Formula: see text], radial distributions of laser-cooled ions (LCIs) and sympathetically cooled ions (SCIs) that do not conform to the rules based on M/Q are realized. The optimum sympathetic-cooling efficiency occurs, where [Formula: see text] is approximately equivalent to [Formula: see text]. These results are applicable to studies such as cold ion clocks, quantum logic manipulation, antimatter synthesis, regulation of cold chemical reaction, and precise spectral measurements based on sympathetic cooling.

LC circuit mediated sympathetic cooling of a proton via image currents

Efficient cooling of trapped charged particles is essential in many fundamental physics experiments, for high-precision metrology, and for quantum technology. Until now, ion-ion coupling for sympathetic cooling or quantum state control has been limited to ion species with accessible optical transitions or has required close-range Coulomb interactions. To overcome this limitation and further develop scalable quantum control techniques, there has been a sustained desire to extend laser-cooling techniques to particles in macroscopically separated traps, opening quantum control techniques to previously inaccessible particles such as highly charged ions, molecular ions, and antimatter particles. Here, we demonstrate sympathetic cooling of a single proton by laser cooled Be+ ions stored in a spatially separated Penning trap. The two traps are connected by a superconducting LC circuit that enables energy exchange over a distance of 9 cm. We simultaneously demonstrate the cooling of a resonant mode of a macroscopic LC circuit with laser-cooled ions and sympathetic cooling of an individually trapped proton, reaching temperatures far below the environment temperature. Importantly, as this technique does not rely on the direct Coulomb interaction but rather on image-current interactions, it can be easily applied to an experiment with antiprotons, facilitating improved precision in matter-antimatter comparisons and dark matter searches.