Quantum estimation methods for quantum illumination

Abstract

5 pags., 2 figs. ; 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. ; The authors acknowledge support from Spanish MINECO/FEDER Grants No. FIS2015-69983-P and No. FIS2015-70856-P, Basque Government Grant No. IT986-16, and UPV/EHU UFI 11/55 and a PhD grant, CAM Research Network QUITEMAD+, Consejería de Educación, Juventud y Deporte, Comunidad de Madrid (S2013/ICE-2801), and the European Project AQuS (Project No. 640800). The authors thank Giuseppe Vitagliano and Iagoba Apellaniz for useful discussions. ; Peer Reviewed