Improving quantum interferometry by using entanglement

We address the use of entanglement to improve the precision of generalized quantum interferometry, i.e., of binary measurements aimed to determine whether or not a perturbation has been applied by a given device. For the most relevant operations in quantum optics, we evaluate the optimal detection strategy and the ultimate bounds to the minimum detectable perturbation. Our results indicate that entanglement-assisted strategies improve the discrimination in comparison with conventional schemes. Possible implementations of entanglement-assisted schemes, in order to approach the performances of the optimal strategies, are also suggested.