Yan-Qing Lu

Light is trapped in a tiny cavity and circles around like a ball in a groove. If you slightly change the material inside, the light notices immediately, and gives a signal. Usually, such sensors work like spring scales: the harder you press, the more noticeable the shift. But there's another, trickier approach: make even a weak perturbation produce a disproportionately large response.

An ordinary random network is like a road map: to connect four cities with a complex interchange, you need to lay down many highways. In the quantum world, things are different.