  Squeezed states of spin systems are an important entangled resource for
quantum technologies, particularly quantum metrology and sensing. Here we
consider the generation of spin squeezed states by interacting the spins with a
dissipative ancillary system. We show that spin squeezing can be generated in
this model by two different mechanisms: one-axis twisting and driven collective
relaxation. We can interpolate between the two mechanisms by simply adjusting
the detuning between the dissipative ancillary system and the spin system.
Interestingly, we find that for both mechanisms, ancillary system dissipation
need not be considered an imperfection in our model, but plays a positive role
in spin squeezing. To assess the feasibility of spin squeezing we consider two
different implementations with superconducting circuits. We conclude that it is
experimentally feasible to generate a squeezed state of hundreds of spins
either by one-axis twisting or by driven collective relaxation.
