  This paper investigates the decoherence effect resulting from the interaction
of squeezed gravitational waves with a system of massive particles in spatial
superposition. This paper investigates the decoherence effect resulting from
the interaction of squeezed gravitational waves with a system of massive
particles in spatial superposition. We first employ the open quantum system
approach to obtain the established decoherence in a spatial superposition of
massive objects induced by squeezed gravitational waves. Subsequently, we focus
on the spin-1/2 particle system, and our analysis reveals that the decoherence
rate depends on both the squeezing strength and the squeezing angle of the
gravitational waves. Our results demonstrate that squeezed gravitational waves
with squeezing strengths of $r_p\geq1.2$ and a squeezing angle of
$\varphi_p=\pi/2$ can induce a 1 % decoherence within 1 s free falling of a
cloud of spin-1/2 particles. This investigation sheds light on the relationship
between squeezed gravitational waves and the coherence of spatial superposition
states in systems of massive particles and their spin. The dependence of
decoherence on squeezing strength and, in the case of spin-$1/2$ particles, on
the squeezing angle paves the way for further exploration and understanding of
the quantum-gravity connection. We suggest that such an experimental setup
could also be employed to eventually investigate the level of squeezing effect
(and hence quantum-related properties) of gravitational waves produced in the
early universe from inflation.
