Fast macroscopic-superposition-state generation by coherent driving

We propose a scheme to generate macroscopic superposition states (MSSs) in spin ensembles, where a coherent driving field is applied to accelerate the generation of macroscopic superposition states. The numerical calculation demonstrates that this approach allows us to generate a superposition of two classically distinct states of the spin ensemble with a high fidelity above 0.97 for 300 spins. For a larger spin ensemble, though the fidelity slightly declines, it maintains above 0.84 for an ensemble of 500 spins. The time to generate an MSS is also estimated, which shows that the significantly shortened generation time allows us to achieve such MSSs within a typical coherence time of the system.