Qufid Advances Quantum Program Fidelity Estimation with Adaptive Measurement Budgets

Key Takeaways

• QuFid adapts measurement budget using circuit DAG analysis
• Incorporates backend noise without prior calibration
• Reduces shots by up to 40% while keeping accuracy
• Uses confidence‑driven early stopping for statistical reliability
• Applicable to varied quantum algorithms via graph representation

Pulse Analysis

Fidelity estimation remains a bottleneck for deploying quantum algorithms on noisy intermediate‑scale quantum (NISQ) hardware. Traditional benchmarking approaches rely on fixed shot counts or learning‑based models that assume static noise profiles, leading to either under‑sampling and inaccurate results or wasteful over‑sampling. As quantum devices become more heterogeneous and their error rates drift over time, a dynamic strategy that accounts for both circuit topology and real‑time hardware conditions is essential for scalable quantum verification.

QuFid addresses this gap by representing quantum programs as directed acyclic graphs (DAGs), where nodes correspond to gates and edges capture non‑commutative dependencies. The framework derives structural deformation metrics—degree shifts, path expansions, and connectivity inflation—to gauge how transpilation reshapes the circuit. These metrics feed into a weighted adjacency matrix that forms a noise‑propagation operator, effectively modeling error diffusion as a Markovian process. An adaptive batch size, calculated as the product of the graph’s spectral complexity and the logarithm of circuit depth, guides the number of measurement shots. The algorithm iteratively gathers data, computes a confidence interval, and stops once the interval falls below a predefined error threshold, ensuring statistical rigor while conserving quantum resources.

Experimental validation on benchmark circuits such as Bernstein‑Vazirani demonstrates that QuFid can slash measurement costs by roughly 40% without sacrificing fidelity precision. By eliminating the need for extensive prior noise characterization, the approach simplifies workflow integration for quantum software developers and cloud providers. Future extensions aim to capture long‑range temporal correlations and to incorporate multi‑objective optimization, including latency and energy consumption. As the quantum ecosystem matures, adaptive, graph‑guided fidelity estimation like QuFid will be pivotal for reliable, cost‑effective quantum computing deployments.