  The realization of ultracold polar molecules in laboratories has pushed both
physics and chemistry to new realms. In particular, these polar molecules offer
scientists unprecedented opportunities to explore chemical reactions in the
ultracold regime where quantum effects become profound. However, a key question
about how two-body losses depend on quantum correlations in an interacting
many-body system remains open so far. Here, we present a number of universal
relations that directly connect two-body losses to other physical observables,
including the momentum distribution and density correlation functions. These
relations, which are valid for arbitrary microscopic parameters, such as the
particle number, the temperature, and the interaction strength, unfold the
critical role of contacts, a fundamental quantity of dilute quantum systems in
determining the reaction rate of quantum reactive molecules in a many-body
environment. Our work opens the door to an unexplored area intertwining quantum
chemistry, atomic, molecular and optical physics, and condensed matter physics.
