5 ms·

First and third paragraphs make strong claims, mentioning forecasts for crypto doomsday scenarios but offering no links. For those of us living under a rock, h

First and third paragraphs make strong claims, mentioning forecasts for crypto doomsday scenarios but offering no links. For those of us living under a rock, how realistic are these applications of quantum computing?

johncolanduoni 10y ago
Realistic in the sense that we will one day have scalable quantum computing? Very. There have been a few (non-crackpot) people in QI and adjacent fields who have argued that it will be impossible indefinitely (one I know of is Gil Kalai), but the consensus that this is physically possible is pretty overwhelming. As to timeframe? Estimates are all over the place but some groups have made promising and somewhat unexpected strides in the last few years (Martini's group at UCSB/Google have done some particularly impressive things). If people in quantum information get extraordinarily lucky, even the more optimistic estimates (usually ~20 years) could be shortened dramatically. Considering how long it takes to roll out totally new crypto, we really should've gotten started yesterday. The biggest complication is that all our quantum-resistant encryption systems are young and untested by crypto standards. We don't want them to be our first line of defense until we have more confidence there won't be some unfortunate way to beat them with a Python script on a laptop in 15 seconds. This seems like a good compromise, especially if they can do it without increasing the number of roundtrips in the handshake (I don't in principle see why they couldn't do both in parallel, but I'm not sure how feasible that is with TLS).
- deleted 10y ago
  [deleted]
- baby 10y ago
  > but the consensus that this is physically possible is pretty overwhelming Most of what I read is "it might happen". No one knows for sure. Most of the claims come from people in need of funding for Quantum research, so this is to take with a grain of salt.
  - jcranmer 10y ago
    As I understand it, the consensus is: 1. Quantum computers do exist in reality, as in we can build qubits, shove them through quantum gates, and read the results. 2. Quantum computers that are large enough to do anything useful don't exist. 3. It's not clear if we can practically build systems that hold 000's of qubits without letting them decohere. 4. D-Wave's quantum computer isn't a quantum computer for the purposes of what most people talk about with quantum computing. It also doesn't look better than classical computers.
  - johncolanduoni 10y ago
    If you didn't read these claims from the clearly biased quantum information researchers (many of whom don't work on or receive grants for anything related to quantum computing, even in grant proposal prose la-la land) then where are you getting your probability assessments from? Not to mention all the physicists who work day-in day-out with quantum mechanics in completely different fields who are also extremely skeptical of the absolute physical impossibility of quantum computing.

johncolanduoni 10y ago

Realistic in the sense that we will one day have scalable quantum computing? Very. There have been a few (non-crackpot) people in QI and adjacent fields who have argued that it will be impossible indefinitely (one I know of is Gil Kalai), but the consensus that this is physically possible is pretty overwhelming. As to timeframe? Estimates are all over the place but some groups have made promising and somewhat unexpected strides in the last few years (Martini's group at UCSB/Google have done some particularly impressive things). If people in quantum information get extraordinarily lucky, even the more optimistic estimates (usually ~20 years) could be shortened dramatically. Considering how long it takes to roll out totally new crypto, we really should've gotten started yesterday. The biggest complication is that all our quantum-resistant encryption systems are young and untested by crypto standards. We don't want them to be our first line of defense until we have more confidence there won't be some unfortunate way to beat them with a Python script on a laptop in 15 seconds. This seems like a good compromise, especially if they can do it without increasing the number of roundtrips in the handshake (I don't in principle see why they couldn't do both in parallel, but I'm not sure how feasible that is with TLS).

deleted 10y ago
[deleted]
baby 10y ago
> but the consensus that this is physically possible is pretty overwhelming Most of what I read is "it might happen". No one knows for sure. Most of the claims come from people in need of funding for Quantum research, so this is to take with a grain of salt.
- jcranmer 10y ago
  As I understand it, the consensus is: 1. Quantum computers do exist in reality, as in we can build qubits, shove them through quantum gates, and read the results. 2. Quantum computers that are large enough to do anything useful don't exist. 3. It's not clear if we can practically build systems that hold 000's of qubits without letting them decohere. 4. D-Wave's quantum computer isn't a quantum computer for the purposes of what most people talk about with quantum computing. It also doesn't look better than classical computers.
- johncolanduoni 10y ago
  If you didn't read these claims from the clearly biased quantum information researchers (many of whom don't work on or receive grants for anything related to quantum computing, even in grant proposal prose la-la land) then where are you getting your probability assessments from? Not to mention all the physicists who work day-in day-out with quantum mechanics in completely different fields who are also extremely skeptical of the absolute physical impossibility of quantum computing.