  Motivated by the experimental realization of quantum spin models of polar
molecule KRb in optical lattices, we analyze the spin 1/2 dipolar Heisenberg
model with competing anisotropic, long-range exchange interactions. We show
that, by tilting the orientation of dipoles using an external electric field,
the dipolar spin system on square lattice comes close to a maximally frustrated
region similar, but not identical, to that of the $J_1$-$J_2$ model. This
provides a simple yet powerful route to potentially realize a quantum spin
liquid without the need for a triangular or kagome lattice. The ground state
phase diagrams obtained from Schwinger-boson and spin-wave theories
consistently show a spin disordered region between the N$\acute{\textrm{e}}$el,
stripe, and spiral phase. The existence of a finite quantum paramagnetic region
is further confirmed by an unbiased variational ansatz based on tensor network
states and a tensor renormalization group.
