A good chef tastes the soup and adds a pinch of salt. Ordinary scales won't notice that pinch, but sensitive ones will. In the quantum world, pairs of entangled particles play the role of such scales. It was previously thought that the entanglement had to be as strong as possible, otherwise precision wouldn't improve. But new work shows that even a weak rubber band between particles is enough.

Physicists took two photons and linked them in a way that allowed them to adjust the strength of the link, much like the tension of a rubber band. Then they used this pair to measure a phase shift in light — much like a chef tasting the soup. They found that even with a weak link, the precision was noticeably better than any instrument without quantum effects. The device could detect that very pinch of salt that ordinary scales would have missed.

The practical benefit is simple: strong entanglement between particles is hard to create and maintain. It breaks apart from the slightest noise. A weak link is easier to sustain — meaning quantum sensors become more accessible. The setup isn't scalable yet, but the next step is to put it on a single chip, like a microchip.

So in the quantum kitchen, you don't always need to boil the broth at maximum heat. Sometimes a gentle simmer is enough to make the soup perfect.