  The internal structure of neutron stars and the physical properties of nuclei
depend on the equation of state (EOS) of neutron matter. Dilute neutron matter
is a quantum system of spin-1/2 Fermi particles interacting via s-wave
scattering. Although a nuclear system and an ultracold atomic system have
length scales and energy scales that differ by several orders of magnitude,
both systems follow a common universal EOS considering their non-dimensional
universal interaction parameters. In this study, we determine the EOS of
neutron matter in the dilute region, where the influence of the s-wave
scattering length is dominant but that of the effective range is small, by
utilizing a quantum simulator of ultracold $^6$Li atoms with Feshbach
resonance.
