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Updated: Jun 1, 2026

A Photonic System for Generating Unconditional Polarization-Entangled Photons Based on Multiple Quantum Interference
Published on: September 5, 2019
Hardy's paradox and violation of a state-independent Bell inequality in time
Alessandro Fedrizzi1, Marcelo P Almeida, Matthew A Broome
1Centre for Engineered Quantum Systems, School of Mathematics and Physics, University of Queensland, 4072 Brisbane, QLD, Australia.
Abstract:
Tests such as Bell's inequality and Hardy's paradox show that joint probabilities and correlations between distant particles in quantum mechanics are inconsistent with local realistic theories. Here we experimentally demonstrate these concepts in the time domain, using a photonic entangling gate to perform nondestructive measurements on a single photon at different times. We show that Hardy's paradox is much stronger in time and demonstrate the violation of a temporal Bell inequality independent of the quantum state, including for fully mixed states.
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