  In quantum mechanical many-body systems, long-range and anisotropic
interactions promote rich spatial structure and can lead to quantum
frustration, giving rise to a wealth of complex, strongly correlated quantum
phases. Long-range interactions play an important role in nature; however,
quantum simulations of lattice systems have largely not been able to realize
such interactions. A wide range of efforts are underway to explore long-range
interacting lattice systems using polar molecules, Rydberg atoms, optical
cavities, and magnetic atoms. Here, we realize novel quantum phases in a
strongly correlated lattice system with long-range dipolar interactions using
ultracold magnetic erbium atoms. As we tune the dipolar interaction to be the
dominant energy scale in our system, we observe quantum phase transitions from
a superfluid into dipolar quantum solids, which we directly detect using
quantum gas microscopy with accordion lattices. Controlling the interaction
anisotropy by orienting the dipoles enables us to realize a variety of stripe
ordered states. Furthermore, by transitioning non-adiabatically through the
strongly correlated regime, we observe the emergence of a range of metastable
stripe-ordered states. This work demonstrates that novel strongly correlated
quantum phases can be realized using long-range dipolar interaction in optical
lattices, opening the door to quantum simulations of a wide range of lattice
models with long-range and anisotropic interactions.
