  Bose-Einstein condensation in strongly correlated lattices provides the
possibility to coherently generate macroscopic quantum states, which have
attracted tremendous attention as ideal platforms for quantum simulation.
Ultracold atoms in optical lattices are one of such promising systems, where
their realizations of different phases of matter exhibit promising applications
in condensed matter physics, chemistry, and cosmology. Nevertheless, this is
only accessible with ultralow temperatures in the nano to micro Kelvin scale
set by the typical inverse mass of an atom. Alternative systems such as
lattices of trapped ions and superconducting circuit arrays also rely on
ultracold temperatures. Exciton polaritons with extremely light effective mass,
are regarded as promising alternatives to realize Bose-Einstein condensation in
lattices at higher temperatures. Along with the condensation, an efficient
exciton polariton quantum simulator would require a strong lattice with robust
trapping at each lattice site as well as strong inter-site coupling to allow
coherent quantum motion of polaritons within the lattice. However, exciton
polaritons in a strong lattice have only been shown to condense at liquid
helium temperatures. Here, we report the observation of exciton polariton
condensation in a one-dimensional strong lead halide perovskite lattice at room
temperature. Modulated by deep periodic potentials, the strong lead halide
perovskite lattice exhibits a large forbidden bandgap opening up to 13.3 meV
and a lattice band up to 8.5 meV wide, which are at least 10 times larger than
previous systems. Above a critical density, we observe exciton polariton
condensation into py orbital states with long-range spatial coherence at room
temperature. Our result opens the route to the implementation of polariton
condensates in quantum simulators at room temperature.
