Hardy's Paradox and Violation of a State-Independent Bell Inequality in Time

Alessandro Fedrizzi (1, 2, 3) , Marcelo P. Almeida (1, 2, 3) , Matthew A. Broome (1, 2, 3) , Andrew G. White (1, 2, 3) , Marco Barbieri (4)

1 EQuS - Centre for Engineered Quantum Systems
2 CQC2T - Centre for Quantum Computer and Communication Technology
3 School of Mathematics and Physics [Brisbane]
4 Laboratoire Charles Fabry de l'Institut d'Optique / Optique quantique

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.

Domains: Quantum Physics [quant-ph]

Alessandro Fedrizzi, Marcelo P. Almeida, Matthew A. Broome, Andrew G. White, Marco Barbieri. Hardy's Paradox and Violation of a State-Independent Bell Inequality in Time. Physical Review Letters, 2010, 106, pp.200402. ⟨10.1103/PhysRevLett.106.200402⟩. ⟨hal-00623078⟩