Quantifying the source of enhancement in experimental continuous variable quantum illumination

A quantum illumination protocol exploits correlated light beams to enhance the probability of detection of a partially reflecting object lying in a very noisy background. Recently a simple photon-number-detection-based implementation of a quantum illumination-like scheme was provided in Phys. Rev. Lett.101, 153603 (2013), where the enhancement was preserved despite the loss of nonclassicality. In the present paper, we investigate the source for quantum advantage in that realization. We introduce an effective two-mode description of the light sources and analyze the mutual information (MI) as a quantifier of total correlations in the effective two-mode picture. In the relevant regime of a highly thermalized background, we find that the improvement in the signal-to-noise ratio achieved by the entangled sources over the unentangled thermal ones amounts exactly to the ratio of the effective MIs of the corresponding sources. More precisely, both quantities tend to a common limit specified by the squared ratio of the respective cross correlations. A thorough analysis of the experimental data confirms this theoretical result.

[1]  S. Olivares,et al.  Full characterization of Gaussian bipartite entangled states by a single homodyne detector. , 2008, Physical review letters.

[2]  Maria Bondani,et al.  Sub-shot-noise photon-number correlation in a mesoscopic twin beam of light , 2007 .

[3]  A. Rényi.  On Measures of Entropy and Information , 1961 .

[4]  C. Fabre,et al.  Entanglement of two-mode Gaussian states: characterization and experimental production and manipulation , 2005, quant-ph/0507067.

[5]  A. De Pasquale,et al.  Discriminating strength: a bona fide measure of non-classical correlations , 2014, 1402.2870.

[6]  Gerardo Adesso,et al.  Continuous Variable Quantum Information: Gaussian States and Beyond , 2014, Open Syst. Inf. Dyn..

[7]  S. Olivares,et al.  Fidelity matters: the birth of entanglement in the mixing of Gaussian states. , 2011, Physical review letters.

[8]  Brian J. Smith,et al.  Real-world quantum sensors: evaluating resources for precision measurement. , 2010, Physical review letters.

[9]  Seth Lloyd,et al.  Gaussian quantum information , 2011, 1110.3234.

[10]  A. Serafini,et al.  Measuring Gaussian quantum information and correlations using the Rényi entropy of order 2. , 2012, Physical review letters.

[11]  Zheshen Zhang,et al.  Entanglement's benefit survives an entanglement-breaking channel. , 2013, Physical review letters.

[12]  Gerardo Adesso,et al.  Gaussian Interferometric Power , 2014, 1406.5857.

[13]  Ou,et al.  Realization of the Einstein-Podolsky-Rosen paradox for continuous variables. , 1992, Physical review letters.

[14]  V. Vedral,et al.  Discord Empowered Quantum Illumination , 2013 .

[15]  A. Gatti,et al.  Correlated imaging, quantum and classical , 2003, quant-ph/0307187.

[16]  Enrico Brambilla,et al.  Correlated imaging, quantum and classical , 2004 .

[17]  Seth Lloyd.  Quantum Illumination , 2008 .

[18]  Marco Genovese,et al.  Measurement of sub-shot-noise spatial correlations without background subtraction. , 2008, Physical review letters.

[19]  F. Illuminati,et al.  Entanglement in continuous-variable systems: recent advances and current perspectives , 2007, quant-ph/0701221.

[20]  G Brida,et al.  Experimental realization of quantum illumination. , 2013, Physical review letters.

[21]  Sammy Ragy,et al.  Unveiling the Hanbury Brown and Twiss effect through Rényi entropy correlations , 2012, 1210.7492.

[22]  Vitus Händchen,et al.  Stable control of 10 dB two-mode squeezed vacuum states of light. , 2013, Optics express.

[23]  Saikat Guha,et al.  Gaussian-state quantum-illumination receivers for target detection , 2009, 0911.0950.

[24]  Davide Girolami,et al.  Quantum Discord Determines the Interferometric Power of Quantum States , 2013, 1309.1472.

[25]  Gerardo Adesso,et al.  Nature of light correlations in ghost imaging , 2012, Scientific Reports.

[26]  S. Lloyd,et al.  Quantum illumination with Gaussian states. , 2008, Physical review letters.

[27]  S. Lloyd.  Enhanced Sensitivity of Photodetection via Quantum Illumination , 2008, Science.

[28]  S. Olivares.  Quantum optics in the phase space A tutorial on Gaussian states , 2012 .

[29]  S. Olivares,et al.  A detailed description of the experimental realization of a quantum illumination protocol , 2013, 1307.3876.

[30]  T. Ralph,et al.  Observing the operational significance of discord consumption , 2012, Nature Physics.

[31]  K. Audenaert,et al.  Discriminating States: the quantum Chernoff bound. , 2006, Physical review letters.

[32]  Seth Lloyd,et al.  Computable bounds for the discrimination of Gaussian states , 2008, 0806.1625.

[33]  G. Brida,et al.  Experimental realization of sub-shot-noise quantum imaging , 2010 .

[34]  Jayne Thompson,et al.  How discord underlies the noise resilience of quantum illumination , 2013, 1312.3332.

[35]  M. Chekhova,et al.  Generation and direct detection of broadband mesoscopic polarization-squeezed vacuum. , 2009, Physical review letters.