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TOPIC:

1k of data in a molecule

2
cypherpunksPerson was signed in when posted
12-01-2002
03:39 PM ET (US)
 This is a technical point, but contrary to the claims in the article it is not possible in quantum mechanics to store and retrieve that much data from the nuclear spins of a single molecule.

Technically, yes, the 19 nuclei can be in any of 2^19 different states. So in principle you can store into one molecule even more than the 1024 bits they used. But you can't read it back at that resolution. You can read maybe 19 bits, but then you've changed the wave function of the molecule and the rest of the data is lost.

What they do is to store the same data in a large number of molecules. Each one is put into the same state, so they are correct to say that the data is put into a single molecule. But their read-back cannot work unless they have a large number of molecules so that they can, in effect, get different data from different molecules.

Here's what they say, from the actual article in the Journal of Chemical Physics: "Therefore, the information is recorded on a single spin cluster, and the other molecules of the sample contain identical copies of the same information. The use of a macroscopic sample was necessary for overcoming the inherently low sensitivity in NMR experiments and suppressing quantum fluctuations, but the sample size can probably be greatly reduced for electron spin systems."

It's not clear that they recognize that there is more to it than instrument sensitivity, or in other words that part of the limitations on what their instruments can do are fundamental aspects of quantum mechanics. They will never be able to do this with a single molecule. It would violate the laws of physics.
1
BuzzPerson was signed in when posted
12-01-2002
09:39 AM ET (US)
 Great idea, but I think we are still very far away from single molecule spectroscopy the way we want to use it. It's a little misleading to say they've stored the data on 1 molecule--it's more like Avogadro's number of molecules or thereabouts (one sample). It may be a long time before we can do NMR spectroscopy with the resolution of individual molecules.
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