Fig. 3

Symmetry-breaking and temporal characteristics of the CBS and CFS peaks. a The experimental CBS (green) and CFS (red) contrasts were measured vs. the parameter \(\tilde \varphi\), which controls the symmetry class. The data are taken at t = 70 kicks, when the CFS contrast approaches that of the CBS. The CBS contrast is maximum at \(\tilde \varphi = - 2\pi {\mathrm{/}}5\), where there is a perfect PT-symmetry. When \(\tilde \varphi\) varies, the CBS contrast decreases, and eventually vanishes when the symmetry is completely broken. Contrary to CBS, the CFS contrast is almost insensitive to the value of \(\tilde \varphi\). The error bars indicate the typical experimental uncertainty. The solid lines are ab initio numerical simulations³³ using experimentally measured parameters. b The time evolutions of the CBS (orthogonal, green) and CFS (orthogonal—red circles, and unitary—red squares) contrasts corresponding to Fig. 2. The CBS follows an exponential decay (dashed green line, fit), due to decoherence, with a fitted time constant t_dec ≈ 190. The CFS contrasts are fitted using the equations in refs. ²² and³⁵ (red lines) with decoherence effects included. This yields t_loc ≈ 40 in the unitary class and t_loc ≈ 37 in the orthogonal class