  It is not clear if the performance of a quantum lidar or radar, without an
idler and only using Gaussian resources, could exceed the performance of a
semiclassical setup based on coherent states and homodyne detection. Here we
prove this is indeed the case by showing that an idler-free squeezed-based
setup can beat this semiclassical benchmark. More generally, we show that
probes whose displacement and squeezing are jointly optimized can strictly
outperform coherent states with the same mean number of input photons for both
the problems of quantum illumination and reading.
