A thin film of silicon nitride is stretched over a frame like the skin of a drum. The slightest nudge from gas molecules makes it tremble. A laser beam delivered through a glass fiber picks up that trembling and turns it into a pressure reading. The whole setup fits in a pocket, not on an optical table.

Previously, such membranes were read with bulky laser interferometers — instruments where light travels through air between mirrors. Now the light is confined within a fiber as thin as a human hair. The sensor was tested in a chamber with a volume of less than a liter, cooled to 78 kelvins (about minus 195 degrees Celsius). Pressure was varied from near-complete vacuum to one ten-thousandth of an atmosphere.

The readout sensitivity reached 8×10⁻¹⁴ meters per root hertz — smaller than the size of an atom. This precision even reveals the thermal jitter of the membrane itself. At room temperature, the response peak is 48 times stronger than this limit; at cryogenic temperatures, it is 25 times stronger.

So the previous range records have not been lost in the transition to fiber. The thin vibrating membrane can now sit in any cryostat, vacuum chamber, or satellite, and quietly report how empty the surroundings are.