google A new hybrid platform for quantum simulation of magnetism (opens in new tab)
Google Quantum AI researchers have developed a hybrid quantum simulation platform that combines the flexibility of digital gates with the high-speed entanglement growth of analog dynamics. Using a 69-qubit Sycamore processor, the team demonstrated high-precision simulations of quantum magnetism that are estimated to be over a million years beyond the reach of the world’s fastest supercomputers. This approach allows for the study of complex physical systems before environmental noise can degrade the quantum state. ## The Hybrid Analog-Digital Approach * Digital simulation provides high flexibility by breaking operations into sequential logical gates, but it is relatively slow because qubits only interact in pairs. * Analog simulation activates all qubit couplers in parallel to mimic continuous, real-world dynamics, enabling much faster growth of quantum entanglement. * The hybrid model uses digital gates for initial state preparation and final characterization, while utilizing analog evolution for the core simulation phase. * This combination minimizes the time the system is exposed to noise while maintaining the ability to target specific, complex problems. ## High-Precision Calibration and Benchmarking * The team overcame the "interference" problem of analog simulation—where simultaneous coupler activation creates unpredictable results—by developing a new calibration scheme and precise hardware modeling. * The system achieved a high level of accuracy, with an error rate of only 0.1% each time a quantum excitation moves between qubits. * Benchmarking via random circuit sampling showed the platform can reach chaotic, highly entangled states significantly faster than purely digital methods. * Researchers estimate that reproducing these results with the same accuracy on the Frontier supercomputer would take more than one million years. ## Discovery in Quantum Magnetism * The researchers used the platform to study the XXZ model, a foundational paradigm in quantum magnetism, across a 69-qubit array. * The experiment investigated how quantum systems reach thermal equilibrium, focusing on the Eigenstate Thermalization Hypothesis (ETH). * The simulation revealed a surprising exception to standard physics theories: a specific parameter regime where the system resisted thermalization and remained in a non-equilibrium state. * This finding challenges the "Generalized Gibbs Ensemble," a widely used theory for predicting the behavior of isolated quantum systems. This hybrid platform establishes a new standard for using current-generation quantum hardware to conduct meaningful scientific research. By integrating analog speed with digital control, the approach provides a viable roadmap for exploring many-body physics and finding practical applications in the NISQ (Noisy Intermediate-Scale Quantum) era.