5 ms·

Upvoting in the hope that someone will explain ... anything about this. The comments so far seem to imply a level of understanding I don't have.

vaidhy 6y ago
Just to be clear, everyone agrees on the advantages of QC and no one disputes that Google has built a quantum computer. Let me try to paraphrase the arguments. 1. QC needs qbits. 1 logical qbit needs many (tens to hundreds) of physical qbits. 2. We need Quantum Error Correction(QEC) to read cleanly from qbits. Current algorithms for QEC need about a 1000 logical qbits. 3. Current state of technology has only 50 - 200 qbits has very low signal to noise and the noise is inherent in the system (you cannot engineer it away) 4. The current systems, specifically Google’s, produce a sequence of numbers. It is possible to have a low complexity algorithm on classical computer which can produce similar sequences (i.e. pass the test for QC produced sequence) 4 is possible because reading from the qbits is noisy and such a noisy data can at best replicate a classical computer. So, the current state of the art, Noisy Intermediate State Quantum computers are not useful for any computation and we need to get to 1000+ qbits to achieve the supremacy. Of course, not everyone agrees that the noise cannot be engineered away or even if the noise is such a big deal.
- crazygringo 6y ago
  Thank you! That's extremely helpful.
McTossOut 6y ago
The argument basically hinges on a claim that losing a single bit at a computation step sticks a wrench in its ability to compute. The claim is the result of a convoluted argument that's hard to read and incomplete. Basically that a more than single bit error collapses a probabilistic computer to a complexity class that can't even multiply. The paper is full of typos, the authors cites himself in his core argument, doesn't relate anything to realized fidelities. It's a very minimally applicable argument to stake a far-reaching claim. Got my attention but, mostly, highlights holes in academic literature and not much else; possibly the author's intent.
ridewinter 6y ago
If anyone is curious on how qubits actually work, I wrote an article explaining from a multiverse perspective: https://medium.com/@dangish/the-quantum-computer-explained-using-the-multiverse-79fa40c96f0a https://medium.com/@dangish/the-quantum-computer-explained-u...

vaidhy 6y ago

Just to be clear, everyone agrees on the advantages of QC and no one disputes that Google has built a quantum computer. Let me try to paraphrase the arguments. 1. QC needs qbits. 1 logical qbit needs many (tens to hundreds) of physical qbits. 2. We need Quantum Error Correction(QEC) to read cleanly from qbits. Current algorithms for QEC need about a 1000 logical qbits. 3. Current state of technology has only 50 - 200 qbits has very low signal to noise and the noise is inherent in the system (you cannot engineer it away) 4. The current systems, specifically Google’s, produce a sequence of numbers. It is possible to have a low complexity algorithm on classical computer which can produce similar sequences (i.e. pass the test for QC produced sequence) 4 is possible because reading from the qbits is noisy and such a noisy data can at best replicate a classical computer. So, the current state of the art, Noisy Intermediate State Quantum computers are not useful for any computation and we need to get to 1000+ qbits to achieve the supremacy. Of course, not everyone agrees that the noise cannot be engineered away or even if the noise is such a big deal.

crazygringo 6y ago
Thank you! That's extremely helpful.

McTossOut 6y ago

The argument basically hinges on a claim that losing a single bit at a computation step sticks a wrench in its ability to compute. The claim is the result of a convoluted argument that's hard to read and incomplete. Basically that a more than single bit error collapses a probabilistic computer to a complexity class that can't even multiply. The paper is full of typos, the authors cites himself in his core argument, doesn't relate anything to realized fidelities. It's a very minimally applicable argument to stake a far-reaching claim. Got my attention but, mostly, highlights holes in academic literature and not much else; possibly the author's intent.

ridewinter 6y ago

If anyone is curious on how qubits actually work, I wrote an article explaining from a multiverse perspective: https://medium.com/@dangish/the-quantum-computer-explained-using-the-multiverse-79fa40c96f0a https://medium.com/@dangish/the-quantum-computer-explained-u...