If quantum computing ever becomes a reality, then what kind of impact will it have on spaceflight?
Quote from: sanman on 04/13/2013 04:35 pmIf quantum computing ever becomes a reality, then what kind of impact will it have on spaceflight?Quantum computing would make many scamgraphy algorithms no longer secure. This could seriously reduce the demand for e.g. satellite phones.Quantum computing may be useful for simulating chemistry, which could potentially lead to advancements in e.g. fuel cells or ISRU. I doubt it would cause nearly as much effect on the space industry as e.g. easy reusability or launch systems owned by non-governments would (will?) have.Quantum computers are not known to be able to solve NP-complete problems in polynomial time, so I do not expect quantum computers to provide more than incremental progress for anything except scamgraphy and simulations of systems where quantum mechanical effects matter. D-Wave is exaggerating its usefulness IMHO.
And there are other, more practical encryption algorithms that can't be trivially cracked by quantum computers. Not everything relies on the difficulty of factoring numbers made of large primes.
Quantum computing is not merely theoretical. It is being done experimentally, though currently it is limited to just a few qubits, so only simple algorithms are being used, and they aren't in danger so far of eclipsing classical computers.
Lowered demand for satellite phones would be the least of your worries.I don't think you realize how much of the modern world is based on the security of encryption.
Quote from: sanman on 04/13/2013 04:35 pmIf quantum computing ever becomes a reality, then what kind of impact will it have on spaceflight?IIRC, according to David Deutsch, a 300-qbits quantum computer could simulate a whole universe. So with quantum computing, we would not have to bother traveling through space because we could explore simulated worlds.(notice that this is one possible answer to the Fermi paradox, btw)
First of all the universe is already quantum mechanical, and it has a lot more qubits.
Quote from: Tass on 04/14/2013 02:48 pmFirst of all the universe is already quantum mechanical, and it has a lot more qubits.Sure, but the universe is not a computer: its particles are not all interconnected. A stack of billions of transistors doesn't make a supercomputer if they are not interconnected.There are about 10^80 atoms in the universe. 2^300 is about 10^90 so Deutsch's idea (I don't remember where I rred it, but it's probably in the fabric of reality, I'll verify one of these days) is not so absurd.Also: yeah, quantum computers can be used only for very specific applications, but simulating physical systems is one of them, IIRC (I recall it was the original idea envisioned by Feynman on the subject, actually).
Do you actually know anything about quantum computing, or only what you heard from blogs and popular science?
I know very little indeed. Happy?
Quote from: grondilu on 04/14/2013 04:05 pmI know very little indeed. Happy?Happy? What do you mean?
I just asked what your basis was. I only have like a quarter year of course work that has directly to do with quantum computing, it is not my field. You seemed insistent that quantum computing could exponentially speed up classical simulation. I had not heard of such an algorithm, but I could possible have missed it.
On the other hand if it is just from blogs and popular science then Occams razor would suggest that the "simulate a universe" thing has been misunderstood or exaggerated somewhere in the chain.
Quote from: Tass on 04/14/2013 05:14 pmQuote from: grondilu on 04/14/2013 04:05 pmI know very little indeed. Happy?Happy? What do you mean?Maybe I'm too susceptible, but I felt a bit of aggressivity in your last question.
I never managed to understand how a quantum computer works, and yet I think I know the basics of quantum mechanics.
What I wrote is that I somewhere rred that David Deutsch thinks a 300-qbits quantum computer could simulate a whole universe. Maybe this is not true, or maybe I misinterpreted the quote. But I thought it was worth mentioning.
We used to use crappier encryption that is now easily crackable. We upgraded. We'll upgrade once more to better algorithms when quantum computing comes online. Not so dramatic.