How to Measure Nothing Better: Quantum Sensors could Support Big Science, Semiconductors, and More

There's no such thing as a complete vacuum. Even in the cosmic void between galaxies, there's an estimated density of about one hydrogen or helium atom per cubic meter. But these estimates are largely theoretical–no one has yet launched a sensor into intergalactic space and beamed back the result. On top of that, we have no means of measuring vacuums that low. ¶ At least, not yet. ¶ Researchers are now developing a new vacuum-measurement tool that may be able to detect lower den-sities than any existing techniques can. This new quantum sensor uses individual atoms, cooled to just shy of absolute zero, to serve as targets for stray particles to hit. These atom-based vacuum measurers can detect lower atomic concentrations than ever before, and they don't require calibration, making them a good candidate to serve as a standard.