A new benchmark measures how well quantum circuits infer charge

Yi-Fan Gong and Dan-Bo Zhang of South China Normal University have developed a new benchmark to measure how well quantum circuits infer conserved charge. Their work extends the study of “charge learnability” to include probabilistic weak measurements, allowing independent tuning of both measurement probability and strength. The researchers found the boundary between successful and unsuccessful charge inference is determined by the informational power of local measurement. “Our results establish informational power of local measurement as a unifying principle for charge learnability under general monitoring protocols,” the paper reports. This work extends beyond previous studies limited to deterministic or purely probabilistic measurements, offering a more detailed understanding of how information is extracted from quantum systems. The researchers specifically focused on U(1)-symmetric circuits, a model system for exploring charge conservation, and how effectively a hidden charge label can be inferred from measurement records. The study introduces cross entropy as a diagnostic tool to…