A Camera That Captures Cold express
At 0.1 K, just three-tenths of a degree above absolute zero, matter stops following the usual rules. Helium becomes superfluid: it flows without friction, seeps through cracks, and behaves like one giant quantum liquid. Seeing what happens inside such cold is a challenge at the edge of possibility.
Scientists have built a device that tackles it head-on. Inside a cryostat, a kind of thermos for extreme cold, sits a rotating platform with a camera. Laser light travels through optical fibers, and images are transmitted through a bundle of one hundred thousand light guides. The resolution is about 30 micrometers, enough to spot details as thin as a human hair.
In one experiment, glowing particles—1 to 6 micrometers in diameter — were launched into liquid helium. They were fired from the surface of a piezoelectric crystal using short vibrations at a frequency of one million times per second. The camera captured particle trajectories at up to 990 frames per second.
This kind of filming reveals how quantum vortices, tiny swirling currents, interact with particles. It's like seeing invisible whirlpools suddenly appear in perfectly still water, pulling everything around them. Previously, these processes were studied indirectly; now they can be observed live.
The device opens the door to studying quantum turbulence — one of the most mysterious areas of physics. Understanding how energy transfers from large vortices to small ones in a superfluid could shed light on processes in neutron stars and even the early universe.
Original abstract
as written by the authors arXiv:2602.21279
We describe a versatile apparatus for optical observations of experimental processes at temperatures down to 0.1 K. The cooling is achieved by a wet cryostat with a dilution refrigerator on a vibrationally-isolated platform, capable of continuous rotation at angular velocity of up to 3 rad/s. The illumination light beam from lasers on a non-rotating optical table at room temperature is introduced via an optical fiber. The images are transferred to the intensified camera at room temperature through a coherent bundle of $$10^5$$ optical fibers giving a spatial resolution of $$\sim 30 \mu$$m, depending on the magnification used. The adjustment of the position of the illumination light, as well as of the focusing of the camera on the object under investigation, can be controlled remotely with the help of piezoelectric positioners. The apparatus was used for visualization of particles dispersed in superfluid helium at temperatures down to 0.14 K. In one version of experiment, fluorescent light from clouds of excimer molecules He$$_2^*$$, generated in liquid helium by electron impact from electrons injected by sharp field-emission tips, was recorded and analyzed. In another, fluorescent particles of diameters between 1 $$\mu$$m and 6 $$\mu$$m were initially loaded onto the horizontal surface of a piezoelectric crystal of LiNbO$$_3$$ and then injected into liquid helium by short bursts of high-amplitude oscillations at the crystal's resonant frequency 1 MHz. The particle trajectories were filmed at a frame rate of up to 990 fps and analyzed.
At 0.1 K, the thermal motion of atoms nearly stops, and helium becomes so fluid that it can leak through pores in glass that won't let ordinary water pass.
In Greg Egan's novel Quarantine, superfluid liquids are used to build quantum computers, and observing vortices in helium echoes the characters' attempts to see hidden structures of reality.