Constraint-Induced Delocalization

We study the impact of quenched disorder on dynamics locally constrained quantum spin chains, that describe 1D arrays Rydberg atoms in both frozen (Ising-type) and dressed ($XY$-type) regime. Performing large-scale numerical experiments, we observe no trace many-body localization even at large disorder. Analyzing role terms systems show they act two, distinct competing ways: as an on-site term for basic excitations system, interaction between excitations. The two contributions are same order, compete (one towards localization, other against it), one does never enter a truly strong disorder, weak limit, where occurs. Such mechanism is further clarified case XY-type models: there, which would represent bona fide local acting clean model must be written series nonlocal unconstrained variables. Our observations provide simple picture to interpret could immediately extended models or gauge theories.