The optimal discrimination of two Gaussian channels is a central problem in quantum information theory. In this talk we discuss how the use of quantum entanglement can reduce the error probability which affects this statistical problem, giving a dramatic advantage over the use of classical light in the regime of few photons.
This enhancement is exploited in two non-trivial tasks: the detection of low-reflectivity targets (quantum illumination [1,2]) and the readout of digital memories (quantum reading ).
 S.-H. Tan et al., Phys. Rev. Lett. 101, 253601 (2008)
 S. Pirandola, and S. Lloyd, Phys. Rev. A 78, 012331 (2008)
 S. Pirandola, arXiv:0907.3398