Demonstrating the power of quantum computers, certification of highly entangled measurements and scalable quantum nonlocality

• Main Authors: Elisa Bäumer, Nicolas Gisin, Armin Tavakoli
• Format: Article
• Language: English
• Published: Nature Publishing Group 2021-07-01
• Series: npj Quantum Information
• Online Access: https://doi.org/10.1038/s41534-021-00450-x

Abstract Increasingly sophisticated quantum computers motivate the exploration of their abilities in certifying genuine quantum phenomena. Here, we demonstrate the power of state-of-the-art IBM quantum computers in correlation experiments inspired by quantum networks. Our experiments feature up to 12 qubits and require the implementation of paradigmatic Bell-State Measurements for scalable entanglement-swapping. First, we demonstrate quantum correlations that defy classical models in up to nine-qubit systems while only assuming that the quantum computer operates on qubits. Harvesting these quantum advantages, we are able to certify 82 basis elements as entangled in a 512-outcome measurement. Then, we relax the qubit assumption and consider quantum nonlocality in a scenario with multiple independent entangled states arranged in a star configuration. We report quantum violations of source-independent Bell inequalities for up to ten qubits. Our results demonstrate the ability of quantum computers to outperform classical limitations and certify scalable entangled measurements.