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Just note that in practice nobody wants to keep their data storing atoms frozen near absolute zero, but rather prefer to have them at temperature close to 300 K.

However to store 1 bit of information at given temperature the energy difference between state corresponding to 0 and state corresponding to 1 has to be not less than something of order kT ≈ 0.02, otherwise the information would be quickly erased by thermal motion. But if we take maximum energy gap at atom that might be used for storing information to be upper bounded by atom's ionization energy [1], it turns out that it can't be larger than something of order 10 eV. So it doesn't seem to be possible to store more than hundreds or thousands of bits per atom at room temperature.

[1] https://en.wikipedia.org/wiki/Ionization_energies_of_the_ele...

Could you please expand on your kT ~ 0.02 calculation?

Sorry, it was of course 0.02 eV, not just 0.02 :)

k = 1.38e-23 J/K = 8.6e-5 eV/K, so kT = 0.025 eV for T = 300 K.

of course ;)

This is an interesting point because with the kind of matter density needed to even approach the Bekenstein bound, it seems like achieving near zero temperatures would be increasingly difficult.

Said another way, the Bekenstein bound is a limit based on the amount of information contained not just in a volume, but also with a given amount of energy. IANATP (I am not a Theoretical Physicist) but it seems like, according to the Bekenstein bound, lowering the temperature might reduce the theoretical amount of information available.

Anyway, yeah, the Bekenstein bound is purely theoretical, there is not, and probably never will be a practical demonstration of it.

> I don't know if we'll see practical atomic storage or if more than one bit per atom is physically possible, but in theory there's enough space in an atom to hold millions of bits.

What will you encode the bits with?

I think he means that physical space could accommodate such number of bits before a black hole forms, not that we can tame an atom specifically to hold that information.

I thought he meant that you could encode more than one of two states. For a very base analogy, instead of just - and | representing 1 and 0, you could have - \ | / representing 00, 01, 10, 11, etc. Wifi does something similar with signal phase.

While I could (and do) definitely have fun speculating that more than two states might be possible to represent - I can imagine a bunch of armchair physics possibilities - I didn't mean to suggest anything specific. The Bekenstein bound is only an idea, there's no known physical way to get even close.

Maybe ionizing states, or bonds using multiple kinds of atoms, or use of radioactive elements, maybe something like that could be used to represent multiple states... I'm sure IBM & other labs are pushing to find out as fast as funding permits.

I can imagine a bunch of armchair physics possibilities

normal caveats (not a physicist, chemist, lawyer, etc)

Since atoms are made of multiple components, if you can modify and measure those components individually, then it's at least theoretically possible to encode more than two states per atom. All of the following assumes you would want to keep the same atomic number for the duration, obviously if you don't care what type of atom you're storing then there would obviously be many more than two states.

If it was possible set and count how many neutrons an particular atom has (aka which isotope), then it would be possible to encode more. Even Hydrogen has three isotopes, and Xenon has nine stable isotopes (and many more unstable). Same for number of electrons (aka ions).

If there are more properties that could be manipulated for each of those individual components, then it would be possible to have even more states. (ex: electron spin).

For example, with a hydrogen atom and it's 3 isotopes, it's theoretically possible to encode 4 states (2^2, half-nibble, crumb)

What about quantum effects? I thought at that scale it would be a qbit.