Light trapped in a tiny cavity is like a pendulum that gets pushed harder and harder. At first, it swings smoothly and predictably, like an ordinary clock. But if you push it hard enough, the motion becomes strange: the pendulum seems to be in two extreme positions at once.
Similarly, photons in a nonlinear resonator: under weak excitation, they behave like a classical wave, but under strong excitation, they become a mixture of two distinct states. The authors of the work found that between these extremes there is a special zone. In this zone, even when some light leaks out, the quantum features do not disappear but instead remain surprisingly persistent.
This is like a tightrope walker balancing with a pole. A light breeze (losses) doesn't knock them off but makes them control their balance more precisely. Such a "breeze" provides a resource for quantum computing that is not afraid of real-world conditions.
Quantum-like models here are not just a metaphor: the mathematics of light behavior in the resonator matches calculations for complex quantum systems. This gives hope that quantum computers based on light could work without perfect isolation from the outside world.
To observe quantum behavior of light, physicists cool the resonator almost to absolute zero — otherwise, thermal fluctuations would drown out the subtle effects.
In the series "Dark," quantum states of particles allow time travel — here, quantum states of light help build machines that compute faster than any supercomputer.