I suspect you are right.

Eventually, I think there is a limit to dat storage, but I believe that limit will be reached in the sub-atomic realm.

I am not sure if such technology is in our grasp at this moment in time. However, using hydrogen atoms and ions as storage should be feasible with today’s technology. The main obstacle I see is how to you make those hydrogen atoms and ions stay put.

For my story I was trying to comprehend how an alien computer might work and just how small their data storage could get. I figured they could do it at the sub-atomic level but I didn’t know how. So I set my sight up to the atomic level and started thinking how we might use atoms as data storage. They hydrogen atom/ion seems like a perfect storage option that we humans could achieve in the near future.

Instead of 0's and 1’s, we now have a third option. This opens the door to more combinations. It is like comparing 2-D to 3-D. So not only is it a smaller storage device, it is also more powerful than the silicon on/off switch.