Violation of the Leggett-Garg inequality with weak measurements of photons

Michael E. Goggin , Marcelo P. Almeida (1, 2, 3) , Marco Barbieri (4) , Benjamin P. Lanyon (3) , Jeremy L. O'Brien (5) , Andrew G. White (1, 2, 3) , Geoff J. Pryde (6)

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
5 Centre for Quantum Photonics
6 Centre for Quantum Dynamics

By weakly measuring the polarization of a photon between two strong polarization measurements, we experimentally investigate the correlation between the appearance of anomalous values in quantum weak measurements and the violation of realism and nonintrusiveness of measurements. A quantitative formulation of the latter concept is expressed in terms of a Leggett-Garg inequality for the outcomes of subsequent measurements of an individual quantum system. We experimentally violate the Leggett-Garg inequality for several measurement strengths. Furthermore, we experimentally demonstrate that there is a one-to-one correlation between achieving strange weak values and violating the Leggett- Garg inequality.

Domaines: Physique Quantique [quant-ph]

Michael E. Goggin, Marcelo P. Almeida, Marco Barbieri, Benjamin P. Lanyon, Jeremy L. O'Brien, et al.. Violation of the Leggett-Garg inequality with weak measurements of photons. Proceedings of the National Academy of Sciences of the United States of America, 2011, 108 (4), pp.1256-1261. ⟨hal-00623095⟩