In this thesis we investigate the theory of quantum hypothesis testing and its potential applications for the new area of quantum technologies. We first consider the asymmetric formulation of quantum hypothesis testing where the aim is to minimize the probability of false negatives and the main tool is provided by the quantum Hoeffding bound. In this context we provide a general recipe for computing this bound in the most important scenario for continuous variable quantum information, that of Gaussian states. We then study both asymmetric and symmetric quantum hypothesis testing in the context of quantum channel discrimination. Here we show how the use of quantum-correlated light can enhance the detection of small variations of transmissivity in a sample of photodegrabable material, while a classical source of light either cannot retrieve information or would destroy the sample. This non-invasive quantum technique might be useful to realize in-vivo and real-time probing of very fragile biological samples, such as DNA or RNA. We also show that the same principle can be exploited to build next-generation memories for the confidential storage of confidential data, where information can be read only by well-tailored sources of entangled light.