Generating highly entangled many-body states on a superconducting processor

Entanglement and its propagation are central to understanding quantum systems. Notably,
within closed interacting many-body systems, entanglement is believed to yield emergent
thermodynamic behavior, yet a universal understanding remains challenging. Quantum
hardware platforms provide a means to study the formation and scaling of entanglement. Here, we use a controllable 4-by-4 array of superconducting qubits to emulate a two-dimensional hard-core Bose-Hubbard lattice. Rather than preparing a definite state, we generate superposition states by simultaneously driving all lattice sites. We extract correlation lengths and entanglement energy for states prepared across the many-body energy spectrum of the lattice, observing volume-law entanglement scaling for states at the center of the spectrum and a crossover to the onset of area-law scaling near its edges. Lastly, we discuss extensions of this state preparation protocol that leverage the dynamic capability of superconducting processors by tracking the propagation of entanglement following a mid-experiment quantum quench.