Quantum mechanics allows the Wigner function — a kind of probability map that sometimes dips into the negative, like a ghost. This indicates that the system is in a superposition (overlapping of states) with no analogue in everyday life. Usually, to induce such 'negativity' in mechanical oscillations, extreme conditions are needed. But physicists found a simpler way: a resonator with nonlinear response acts like a curved mirror. A short laser pulse, reflecting, distorts and 'winds' quantum weirdness onto the motion — and now Wigner negativity emerges without extra tricks.

This is fuel for quantum computers and algorithms, a resource for quantum information. Moreover, the method promises to simplify detectors for gravitational waves, invented by Rainer Weiss — there they also struggle with quantum uncertainty and loss of quantum properties. The works of David Wineland and Serge Haroche inspired the authors and helped to lower the requirements for the experiment.