  We present quantitative predictions for quantum simulator experiments on
Ising models from trapped ions to Rydberg chains and show how the
thermalization, and thus decoherence times, can be controlled by considering
common, independent, and end-cap couplings to the bath. We find (i) independent
baths enable more rapid thermalization in comparison to a common one; (ii) the
thermalization timescale depends strongly on the position in the Ising phase
diagram; (iii) for a common bath larger system sizes show a significant slow
down in the thermalization process; and (iv) finite-size scaling indicates a
subradiance effect slowing thermalization rates toward the infinite spin chain
limit. We find it is necessary to treat the full multi-channel Lindblad master
equation rather than the commonly used single-channel local Lindblad
approximation to make accurate predictions on a classical computer. This method
reduces the number of qubits one can practically classical simulate by at least
a factor of 4, in turn showing a quantum advantage for such thermalization
problems at a factor of 4 smaller qubit number for open quantum systems as
opposed to closed ones. Thus, our results encourage open quantum system
exploration in noisy intermediate-scale quantum technologies.
