  We propose an efficient stepwise adiabatic merging (SAM) method to generate
many-body singlet states in antiferromagnetic spin-1 bosons in concatenated
optical superlattices with isolated double-well arrays, by adiabatically
ramping up the double-well bias. With an appropriate choice of bias sweeping
rate and magnetic field, the SAM protocol predicts a fidelity as high as 90%
for a sixteen-body singlet state and even higher fidelities for smaller
even-body singlet states. During their evolution, the spin-1 bosons exhibit
interesting squeezing dynamics, manifested by an odd-even oscillation of the
experimentally observable squeezing parameter. The generated many-body singlet
states may find practical applications in precision measurement of magnetic
field gradient and in quantum information processing.
