Speaker: Ana Alonso-Serrano (HU Berlin)

Title:Quantum estimation of cosmological parameters

Abstract:
Understanding how well future cosmological experiments can reconstruct the mechanism that generated primordial inhomogeneities is key to assessing the extent to which cosmology can inform fundamental physics. In this talk, I will introduce (in a simple, conceptual manner) a recent work where we apply a quantum metrology tool — the quantum Fisher information — to the squeezed quantum state describing cosmological perturbations at the end of inflation. This quantifies the ultimate precision achievable in parameter estimation, assuming ideal access to early-universe information, and then we evaluate how close current observations come to this quantum limit. Focusing on the tensor-to-scalar ratio as a case study, we found that the existence of a highly efficient (but presently inaccessible) optimal measurement. Conversely, I will show that accessing the decaying mode of inflationary perturbations is a necessary condition for exponentially improving the inference of the tensor-to-scalar ratio.