4 ms·
Quantum teleportation cant transport data faster than light, but something very similar which looks more useful in terms of daily needs is superdense coding [0]
by up6w6 6y ago
Quantum teleportation cant transport data faster than light, but something very similar which looks more useful in terms of daily needs is superdense coding [0]. Basically you could encode two bits as one qubit, which looks like some type of "physical compression" and the algorithm is almost the same as teleportation.
[0]: https://en.wikipedia.org/wiki/Superdense_coding https://en.wikipedia.org/wiki/Superdense_coding
- ajuc 6y agoIsn't that the same as just using 4 voltages (or any other analog property) instead of 2 to encode 2 bits instead of 1? Qbits are analog so it's no surprise it can be done with them as well. Flash memory already does that in classical chips. There's nothing preventing you from going further - 8 voltages for 3 bits etc.
- waterhouse 6y agoAnd classical bits are presumably much easier to transport intact, by several orders of magnitude in terms of cost. Seems the superdense coding would only help if sending qubits were less than 2x as expensive as sending classical bits.
- tsimionescu 6y agoThe problem with analog encodings is that it often doesn't scale at all - the energy required to measure your analog state precisely enough to send large numbers of bits becomes too impractical.
- nynx 6y agoI remember reading a paper somewhere (can't find it now) on how it should be possible to compress N bits of data into log2(N) qubits. This would be utterly transformative since you could then compress basically any amount of data into just a few qubits (e.g. 1e15 bits would fit in ~50 qubits).
- whatshisface 6y agoYou're not going to get that data back out, though. When you measure 50 qbits, you get 50 bits, and you destroy the state irrecoverably.
- nynx 6y agoYeah, I think whether extraction was possible was up in the air. I believe it mentioned that quantum RAM could let you store that data and operate upon it.
- deleted 6y ago[deleted]
- tsimionescu 6y agoPer the wikipedia page, the protocol provides both encoding and decoding, and there have been experimental realizations that successfully retrieved the original message. Is the article inaccurate?
- whatshisface 6y agoThe parent comment was talking about data compression, the article is talking about copying a quantum state. Data compression will not work because you can't read a quantum state into classical information.
- tsimionescu 6y agoThe article on superdense coding that started this mini thread [0] talks about a protocol for sending 2 bits of information as 1 qubit, and recovering the 2 bits on the receiver side. More specifically, it seems that actually there are 2 shared qubits - one half of an entangled pair ahead of time; and one additional qubit when the message is decided. While 0 information can be transmitted using the entangled pair, entangled qubit + 1 qubit leads to 2 classical bits of information. [0] https://en.wikipedia.org/wiki/Superdense_coding https://en.wikipedia.org/wiki/Superdense_coding