Open quantum systems for quarkonia

I review recent applications of the open quantum system framework in understanding quarkonium suppression heavy-ion collisions, which has been used as a probe quark-gluon plasma for decades. The derivation Lindblad equations both Brownian motion and optical limits their semiclassical counterparts is explained. hierarchy time scales assumed justified from separation energy nonrelativistic effective field theories QCD. Physical implications approach are also discussed. Finally, list some questions future studies.