Quantum many-body dynamics on the star graph

Understand

We study 2-local Hamiltonian quantum systems, consisting of qubits interacting on the star graph of N vertices.

• We numerically demonstrate that these models are generically non-integrable at infinite temperature, and find evidence for a finite temperature phase transition to a glassy phase in generic models.
• Operators can become complicated in constant time: we explicitly find that there is no bound on out-of-time-ordered correlators, even at finite temperature.
• Operator growth is not correctly modeled by stochastic quantum dynamics, including Brownian Hamiltonian dynamics or random unitary circuits.