Abstract
Superposition, entanglement and non-locality constitute fundamental features of quantum physics. The fact that quantum physics does not follow the principle of local causality can be experimentally demonstrated in Bell tests performed on pairs of spatially separated, entangled quantum systems. Although Bell tests, which are widely regarded as a litmus test of quantum physics, have been explored using a broad range of quantum systems over the past 50 years, only relatively recently have experiments free of so-called loopholes succeeded. Such experiments have been performed with spins in nitrogen–vacancy centres, optical photons and neutral atoms. Here we demonstrate a loophole-free violation of Bell’s inequality with superconducting circuits, which are a prime contender for realizing quantum computing technology. To evaluate a Clauser–Horne–Shimony–Holt-type Bell inequality4, we deterministically entangle a pair of qubits and perform fast and high-fidelity measurements along randomly chosen bases on the qubits connected through a cryogenic link spanning a distance of 30 metres. Evaluating more than 1 million experimental trials, we find an average S value of 2.0747 ± 0.0033, violating Bell’s inequality with a P value smaller than 10−108. Our work demonstrates that non-locality is a viable new resource in quantum information technology realized with superconducting circuits with potential applications in quantum communication, quantum computing and fundamental physics. Show more
Permanent link
https://doi.org/10.3929/ethz-b-000612915Publication status
publishedExternal links
Journal / series
NatureVolume
Pages / Article No.
Publisher
NatureOrganisational unit
03720 - Wallraff, Andreas / Wallraff, Andreas
02205 - FIRST-Lab / FIRST Center for Micro- and Nanoscience
Funding
899354 - Quantum Local Area Networks with Superconducting Qubits (EC)
Related publications and datasets
Is supplemented by: https://doi.org/10.3929/ethz-b-000624026
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