Homodyne estimation of Gaussian quantum discord

Rémi Blandino (1) , Marco G. Genoni (2) , Jean Etesse (1) , Marco Barbieri (1) , Matteo G. A. Paris (3, 4) , Philippe Grangier (1) , Rosa Tualle-Brouri (5, 1)

1 Laboratoire Charles Fabry / Optique Quantique
2 Quantum Optics and Laser Science, Blackett Laboratory
3 Dipartimento di Fisica (Milano)
4 CNISM - UdR Milano
5 IUT de Cachan

We address the experimental estimation of Gaussian quantum discord for two-mode squeezed thermal state, and demonstrate a measurement scheme based on a pair of homodyne detectors assisted by Bayesian analysis which provides nearly optimal estimation for small value of discord. Besides, though homodyne detection is not optimal for Gaussian discord, the noise ratio to the ultimate quantum limit, as dictacted by the quantum Cramer-Rao bound, is limited to about 10 dB.

Domains: Quantum Physics [quant-ph]

Rémi Blandino, Marco G. Genoni, Jean Etesse, Marco Barbieri, Matteo G. A. Paris, et al.. Homodyne estimation of Gaussian quantum discord. Physical Review Letters, 2012, 109 (18), pp.180402. ⟨10.1103/PhysRevLett.109.180402⟩. ⟨hal-00676458v3⟩