  The field of quantum sensing aims at improving the detection and estimation
of classical parameters that are encoded in physical systems by resorting to
quantum sources of light and quantum detection strategies. The same approach
can be used to improve the current classical measurements that are performed on
biological systems. Here we consider the scenario of two bacteria (E. coli and
Salmonella) growing in a Luria Bertani broth and monitored by classical
spectrophotometers. Their concentration can be related to the optical
transmissivity via the Beer-Lambert-Bouguer's law and their growth curves can
be described by means of Gompertz functions. Starting from experimental data
points, we extrapolate the growth curves of the two bacteria and we study the
theoretical performance that would be achieved with a quantum setup. In
particular, we discuss how the bacterial growth can, in principle, be tracked
by irradiating the samples with orders of magnitude fewer photons, identifying
the clear superiority of quantum light in the early stages of growth. We then
show the superiority and the limits of quantum resources in two basic tasks:
(i) the early detection of bacterial growth and (ii) the early discrimination
between two bacteria species.
