Thermalization and Criticality on an Analog-Digital Quantum Simulator, Part 2: benchmarking

Achieving quantum simulations of complex physical phenomena that are intractable for classical computers is a major milestone in quantum computing. We demonstrate such a regime by studying the analog time-evolution of a 2D XY spin model implemented on a 69-qubit quantum processor. To accurately benchmark this evolution, we introduce a novel and scalable calibration technique specifically designed for analog quantum simulation. Our experiments, validated by cross-entropy benchmarking at systems up to 35 qubits, exhibit error rates under 0.1% per qubit per cycle, rapid entanglement saturation and convergence to a robust Porter-Thomas bitstring distribution.

The combination of fast dynamics and low error rates results in a very pure and entangled state quantified by the maximum reached mixed-state entanglement entropy. This combination ensures high computational complexity even using state-of-the-art classical techniques.