Topics: CERN, Condensed Matter Physics, Entanglement, Lasers, Quantum Mechanics
Much of modern experimental physics relies on a counterintuitive principle: Under the right circumstances, zapping matter with a laser doesn’t inject energy into the system; rather, it sucks energy out. By cooling the system to a fraction of a degree above absolute zero, one can observe quantum effects that are otherwise invisible.
Laser cooling works like a charm, but only when a system’s ladder of quantum states is just right. Atoms of alkali metals and a few other elements are ideal. Molecules, with their multitudes of energy levels, pose a much greater challenge. And fundamental particles such as protons, which lack internal states altogether, can’t be laser-cooled at all.
Nevertheless, there’s a lot of interest in experimenting on protons at low temperature—in particular, precisely testing how their mass, magnetic moment, and other properties compare with those of antiprotons. Toward that end, the Baryon Antibaryon Symmetry Experiment (BASE) collaboration has now demonstrated a method for using a cloud of laser-cooled beryllium ions to sympathetically cool a single proton, even when the proton and ions are too distant to directly interact.
A superconducting circuit is a cooling teleporter, Johanna L. Miller, Physics Today