This team has made a nonlinear lattice that relies on something they call "Joule-Thomson-like expansion." The Joule-Thomsen effect is the ideal gas law in beginning science. PV=nRT. Compression heats a gas, expansion cools a gas.
Why they're studying the equivalent photonics principle [1] is that it focuses an array of inputs, "causing light to condense at a single spot, regardless of the initial excitation position." Usually the problem is that light is linearly independent: two beams blissfully ignore each other. To do useful switching or compute, one of the beams has to be able to act as a control signal.
A photon gas doesn't conserve the number of particles (n) like beginning physics would suggest. This lets the temperature of the gas control the output.
The temperature, driven by certain specific inputs, produces the nonlinear response. I didn't see a specific claim what gain they achieved.
This paper is more on the theoretical end of photonics research. Practical research such as at UBC Vancouver [2] where a device does "weight update speed of 60 GHz" and for clustering it can do "112 x 112-pixel images" - the tech doesn't compete well against electronics yet.
TSMC and NVidia are attempting photonics plays too. But they're only achieving raw I/O with photons. They can attach the fiber directly to the chip to save watts and boost speeds.
Basic physics gets in the way too. A photon's wavelength at near UV is 400 nanometers, but the transistors in a smartphone are measured at 7 nanometers ish. Electrical conduction is fundamentally smaller than a waveguide for light. Where light could maybe outshine electrons is in switching speed. But this research paper doesn't claim high switching speed.