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by daxfohl 2001 days ago
No, nothing. The only thing that a real machine is useful for now is testing that the machine works. Other than google's recent contrived test, any quantum algorithm ever executed will run just as well (or better) on a simulator as on a real machine.

It's going to be like that for a while, even after we're well into the quantum supremacy realm. First, there's not anything you can do with a real machine until error correction is working, which requires 10k(?) qubits. And frankly, there isn't a whole lot you could do with even a real million qbit machine now if one were to exist. Prime factorization is the big one, but other NP complete problems have no known quantum algorithm to speed them up (and note prime factorization is not NP complete -- so it's possible no quantum speedup for any NP complete problem exists (or it's possible that P==NP in which case....)). The real work is in the math and algo theory to find solutions for these problems. Coding and running them is actually kind of incidental and "cute".
3 comments
hilbertseries 2001 days ago
> And frankly, there isn't a whole lot you could do with even a real million qbit machine now if one were to exist.

Aside from being able to break the majority of asymmetric encryption schemes, in particular RSA as you mention with prime factoring.

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kart23 2001 days ago
Mining bitcoin would be a good use, right? Probably would be able to break even on the cost.
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gbh444g 2001 days ago
In addition to that, Stephen Wolfram hypothesized that QC won't be possible because with the growth of QC state, the energy required for error correction will grow just as fast, so the theoretical exponential speedup will require exponentially more energy, and this is why the today's QC devices has to split QC bits into small groups.
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tsimionescu 2001 days ago
Many people hypothesize similar things, but there is as yet no real reason behind these hypotheses.

Still, it would be an extremely exciting discovery for physics if it turned out that a QC is not physically realizable. It would prove that quantum mechanics is not the final description of the world, and it would likely be a huge step forward for understanding the measurement problem.

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