Image-Current Mediated Sympathetic Laser Cooling of a Single Proton in a Penning Trap Down to 170 mK Axial Temperature
The BASE collaboration at CERN have set a new temperature record for cooling a single proton, achieving a temperature of just 170 mK.
This breakthrough, which was reported in Physical Review Letters, was accomplished using a novel technique called image-current mediated sympathetic cooling. The temperature achieved is a 15 fold improvement on the previous record so this new achievement represents a significant improvement.
The new technique involves using two independent Penning traps to confine a single proton in one and a beryllium ion in the other. The beryllium ion is then cooled using lasers, and the cold ion transfers its energy to the proton through the interaction of their electric fields. This process, known as sympathetic cooling, allows the proton to be cooled to an extremely low temperature.
This new technique is significant because it could be used to cool other types of particles, such as antiprotons and electrons. This could lead to new experiments in particle physics and quantum mechanics such as CPT reversal symmetry tests via magnetic moment and charge-to-mass ratio measurements with protons and antiprotons, magnetic moment measurements of light nuclei, tests of quantum electrodynamics via precision (mass) spectroscopy of highly charged ions, tests of the electroweak force with single molecular ions, as well precision mass measurements of radioactive ions.
Cooling schemes which rely on image-current coupling can in principle be applicable to any trapped charged particle and experimental systems beyond Penning traps. In particular, once even lower temperatures of about 10 mK (axial) can be reached, the sympathetic cooling will significantly boost the sampling rate and spin state detection fidelity of future 𝑔-factor measurements on protons, antiprotons, and other nuclear moments, as well as reduce the dominant systematic uncertainties in mass measurements with the highest precision.
For further information please see the original paper: C. Will et al. (BASE Collaboration), Image-Current Mediated Sympathetic Laser Cooling of a Single
Proton in a Penning Trap Down to 170 mK Axial Temperature, Phys. Rev. Lett. 133, 023002, DOI: https://doi.org/10.1103/PhysRevLett.133.023002
Feature image: (a) Schematic of the experimental setup. A cloud of beryllium ions is trapped in the loading trap (LT) and a single proton in the proton trap (PT). Both traps are connected to a common resonator. The proton is transported from the PT into the temperature measurement trap (TMT) for measuring its modified cyclotron energy via a quadratic magnetic field inhomogeneity. (b) Typical Boltzmann distribution of a temperature measurement. The red line corresponds to the Boltzmann distribution with a temperature as determined by the maximum-likelihood method