Bo Liu

An ordinary free-electron laser is like a musical instrument with a single string: it can play only one note until you change its design. To get a different wavelength, you have to retune magnets or accelerate electrons harder. That's expensive and bulky.

Standard optical fiber is like a glass thread that carries light. But when you send weak quantum signals (individual photons) and powerful classical laser light through it at the same time, trouble arises. The glass slightly scatters light: this is called Raman scattering.

Ruthenium oxide has long been regarded as a textbook altermagnet — a material where magnetic moments of neighboring atoms point in opposite directions but do not fully cancel due to the crystal's special symmetry. New measurements show that inside the crystal, there is no magnetism at all. All the magnetic action is confined to the surface.

Deep inside the atomic nucleus of thorium-229, there's a stiff lever. To flip it from one position to another, you need to apply force, and that usually takes time. This isotope has two very close energy levels, and the transition between them can be triggered by a laser pulse.

In brachytherapy, thin catheters are inserted into tumors. On CT scans, they look like tangled glowing threads. Previously, doctors would manually outline each one, spending up to an hour. The new algorithm learns from synthetic scans — drawing metal strips in an empty volume, like threads without a body.

A shooter aims at a target, pulls the trigger, and hears two shots: one loud, one quiet. That's how the new setup works, except instead of bullets, there's an electron bunch, and instead of shots, there are two flashes of light. One flash is X-ray, the other is terahertz. They fly to the same point with perfect timing.

A hydrogen bubble on a platinum electrode behaves like a swimmer trying to surface, but every time it almost breaks free, something below grabs its legs. In the lab, high-speed cameras captured this behavior: a millimeter-sized bubble hangs near the surface, even though buoyancy pulls it upward with a force thousands of times stronger than surface tension can hold.