  Strongly correlated quantum matter -- such as interacting electron systems or
interacting quantum fluids -- possesses properties that cannot be understood in
terms of linear fluctuations and free quasi-particles. Quantum fluctuations in
these systems are indeed large and generically exhibit non-Gaussian statistics
-- a property captured only by inspecting high-order correlations, whose
quantitative reconstruction poses a formidable challenge to both experiments
and theory alike. A prime example of correlated quantum matter is the strongly
interacting Bose fluid, realized by superfluid Helium and, more recently,
ultra-cold atoms. Here, we experimentally study interacting Bose gases from the
weakly to the strongly interacting regime through single-atom-resolved
correlations in momentum space. We observe that the Bogoliubov pairing among
modes of opposite momenta, emblematic of the weakly interacting regime, is
suppressed as interactions become stronger. This departure from the predictions
of Bogoliubov theory signals the onset of the strongly correlated regime, as
confirmed by numerical simulations that highlight the role of non-linear
quantum fluctuations in our system. Additionally, our measurements unveil a
non-zero four-operator cumulant at even stronger interactions, which is a
direct signature of non-Gaussian correlations. These results shed light on the
emergence and physical origin of non-Gaussian correlations in ensembles of
interacting bosons.
