title: Quantum Estimation Methods for Quantum Illumination.
abstract: Quantum illumination consists in shining quantum light on a target region immersed in a bright thermal bath with the aim of detecting the presence of a possible low-reflective object. If the signal is entangled with the receiver, then a suitable choice of the measurement offers a gain with respect to the optimal classical protocol employing coherent states. Here, we tackle this detection problem by using quantum estimation techniques to measure the reflectivity parameter of the object, showing an enhancement in the signal-to-noise ratio up to 3 dB with respect to the classical case when implementing only local measurements. Our approach employs the quantum Fisher information to provide an upper bound for the error probability, supplies the concrete estimator saturating the bound, and extends the quantum illumination protocol to non-Gaussian states. As an example, we show how Schrödinger's cat states may be used for quantum illumination.
authors.affiliation: Department of Physical Chemistry, University of the Basque Country UPV/EHU, Apartado 644, 48080 Bilbao, Spain.
authors.forename: M
authors.initials: M
authors.lastname: Sanz
authors.affiliation: Department of Physical Chemistry, University of the Basque Country UPV/EHU, Apartado 644, 48080 Bilbao, Spain.
authors.forename: U
authors.initials: U
authors.lastname: Las Heras
authors.affiliation: Instituto de Física Fundamental IFF-CSIC, Calle Serrano 113b, 28006 Madrid, Spain.
authors.forename: J J
authors.initials: JJ
authors.lastname: García-Ripoll
authors.affiliation: Department of Physical Chemistry, University of the Basque Country UPV/EHU, Apartado 644, 48080 Bilbao, Spain.|IKERBASQUE, Basque Foundation for Science, Maria Diaz de Haro 3, 48011 Bilbao, Spain.
authors.forename: E
authors.initials: E
authors.lastname: Solano
authors.affiliation: Department of Physical Chemistry, University of the Basque Country UPV/EHU, Apartado 644, 48080 Bilbao, Spain.|Dahlem Center for Complex Quantum Systems, Freie Universität Berlin, 14195 Berlin, Germany.
authors.forename: R
authors.initials: R
authors.lastname: Di Candia