  Yang-Lee edge singularities are the branch point of the free energy on the
complex plane of physical parameters and were shown to be the simplest
universality class of phase transitions. However, the Yang-Lee edge
singularities have not been regarded as experimentally observable since they
occur at complex physical parameters, which are unphysical. A recent discovery
about the relation between partition functions and probe spin coherence makes
it experimentally feasible to access the complex plane of physical parameters.
However, how to extract the critical point and the critical exponent of
Yang-Lee edge singularities in many-body systems, which occurs only at
thermodynamic limit, has still been elusive. Here we show that the quantum
coherence of a probe spin coupled to finite-size Ising-type spin systems
presents universal scaling behavior near the Yang-Lee edge singularity. The
finite-size scaling behavior of quantum coherence of the probe spin predicts
that one can extract the critical point and the critical exponent of the
Yang-Lee edge singularity of Ising-type spin system in the thermodynamic limit
from the spin coherence measurement of the probe spin coupled to finite
Ising-type spin systems. This finding provides a practical approach to studying
the nature of Yang-Lee edge singularities of many-body systems.
