Credit: Image credit: S. Kelley/JQI
(1) Using a laser, the ion spin chain is optically pumped to a spin state that is uncorrelated with respect to the spin-spin interactions. (2) The system is suddenly perturbed by lasers, turning on global spin-spin interaction. (3) After the spin system evolves for various lengths of time (t1…tn), the spin state of each ion is captured with a CCD camera. The researchers can directly observe the spin-spin correlations propagating across the ion chain.