Light and matter in the tiny world obey laws that are hard to compute even on a supercomputer. Physicists build special "quantum simulators"—setups where cold atoms play the roles of particles and fields. But until now, such simulators could only depict the field in its simplest form: as if it were either present or absent. Real light, however, has an infinite number of shades.
The new work proposes a simulator where the field can take three different states. Atoms are arranged in a lattice of laser beams, slightly tilted like a staircase with uneven steps. This makes the atoms interact in such a way that the required combinations are preserved on their own — much like water in communicating vessels always levels out. This "protective mechanism" prevents the system from straying off the correct path.
Tests on a computer model showed that even under abrupt changes in conditions, the system continues to accurately follow the laws of electrodynamics. This opens the way to more realistic quantum simulations where light and matter interact in full detail.
Cold atoms in such setups are cooled to millionths of a degree above absolute zero — at this temperature they almost freeze and become obedient.
The idea of a quantum simulator echoes the "reality computer" from Stanislaw Lem's story, where physical processes replace mathematical calculations.