## Abstract

Quantum mechanics can produce correlations that are stronger than classically allowed. This stronger–than–classical correlation is the “fuel” for quantum computing. In 1991 Schumacher forwarded a beautiful geometric approach, analogous to the well-known result of Bell, to capture non-classicality of this correlation for a singlet state. He used a well-established information distance defined on an ensemble of identically–prepared states. He calculated that for certain detector settings used to measure the entangled state, the resulting geometry violated a triangle inequality — a violation that is not possible classically. This provided a novel information–based geometric Bell inequality in terms of a “covariance distance.” Here we experimentally reproduce his construction and demonstrate a definitive violation for a Bell state of two photons based on the usual spontaneous parametric down-conversion in a paired BBO crystal. The state we produced had a visibility of V_{ad}=0.970. We discuss generalizations to higher dimensional multipartite quantum states.

Original language | English |
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Article number | 127444 |

Journal | Physics Letters, Section A: General, Atomic and Solid State Physics |

Volume | 405 |

DOIs | |

State | Published - 30 Jul 2021 |

## Keywords

- Quantum entanglement
- Quantum mechanics