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.
Highlights
Quantum computers have developed rapidly in recent years, with remarkable improvements in control, quality and scale
While the presently available quantum computers have been used for realising many protocols and algorithms in quantum theory, it is interesting and important to consider the ability of such devices to realise predictions of quantum theory that cannot be explained by any conceivable classical model
We have reported demonstrations of quantum predictions that defy general classical models in scalable experiments featuring up to ten qubits in which the central component is the implementation of sophisticated entangled measurements of many qubits
Summary
Quantum computers have developed rapidly in recent years, with remarkable improvements in control, quality and scale. The last decade has seen much attention directed at more sophisticated correlation experiments performed in quantum networks. These networks feature several parties that are connected through a given topology which may feature entangled states or quantum communication channels. In contrast to e.g. traditional Bell experiments, entangled measurements (i.e. projections of several distinct qubits onto an entangled basis) are indispensable to understanding and realising quantum correlations in networks. The paradigmatic Bell-State Measurement (BSM), known from quantum teleportation[7] and entanglement-swapping[8], is at the heart of many schemes for quantum correlations in networks (see e.g.9–12) For the simplest network, quantum nonlocality has recently been experimentally demonstrated on optical platforms[13,14,15]
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