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Consider a classical computer, one making, say, a calculation involving a large amount of data. Would quantum memory allow it to store that information (in the short term) more efficiently, or better handle that quantity of data?

My thought would be it isn't possible, due to the advantage of quantum information storage being in the superpositions, and the data from a classical computer being very much not in a superposition, but I'd like to see if this is correct.

Either way, citations for further reading would be much appreciated.

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1 Answers1

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In summary, no.

If you think about it, this makes sense. When measuring a quantum system with $n$ qubits, you get $n$ bits of information. the $2^n$ figure exists only when the system is in superposition, which a classical computer cannot access.

The specific theorem in question here is Holevo's theorem. To quote Wikipedia:

In essence, the Holevo bound proves that given $n$ qubits, although they can "carry" a larger amount of (classical) information (thanks to quantum superposition), the amount of classical information that can be retrieved, i.e. accessed, can be only up to $n$ classical (non-quantum encoded) bits.

See this physics question and answer(s) as well. (Thanks to glS for linking to this in the comments.)

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