Cyril Elouard

A quantum state under continuous measurement is not a frozen picture but a random dance. Each measurement outcome nudges the state one way or another, and to predict the future you have to track the entire trajectory.

Picture a closed door with a keyhole. Behind it lies the quantum world, full of details that cannot be taken in all at once. Through the keyhole you see only a narrow beam of light picking out a few features. Thermodynamics works the same way: an observer can measure not everything, but only a handful of quantities, such as temperature, pressure, and volume.