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I am out of the loop, are there any "real" quantum computers yet? I was under the impression that no one was really making actual quantum computers yet, but som

I am out of the loop, are there any "real" quantum computers yet? I was under the impression that no one was really making actual quantum computers yet, but some sort of annealing machine like d-wave. Are these IBM machines finally "real" quantum computers?

obastani 9y ago
D-Wave is not a "real" quantum computer in the sense that it is not asymptotically faster than a classical computer. Quantum computers with very few Quibits have existed for a while -- I believe the current record is 17 quibits [1]. I believe that to factor an n-bit integer, you need roughly n bits. So right now, we can factor 17 bit integers, which isn't very useful yet. However, I have read that for quantum simulations, it 30 quibit quantum computers might already be useful. [1] https://en.wikipedia.org/wiki/Timeline_of_quantum_computing https://en.wikipedia.org/wiki/Timeline_of_quantum_computing
- krastanov 9y ago
  It is worse than that. To factor n bit number you need roughly n "logical" qubits, i.e. qubits that can store information almost indefinitely. The quantum computers that we have contain low quality "physical" qubits that lose their content after a few millisecond. You need to put an error correcting code on top of the physical qubits to encode the logical qubits. You can expect to need 100s or 1000s of physical qubits per logical qubit. I.e. to decode modern public key encryption you need a computer with millions of qubits. Today we have less than 50 in the best research hardware on the planet.
  - gaze 9y ago
    Or a good cavity or two.
  - marcosdumay 9y ago
    This one I don't get. Isn't "a few milliseconds" more than enough time to gather a guess on integer factorization (and most of the useful problems)? Wouldn't it suffice to run your program again and again over the same short-lived qubits?
mtgx 9y ago
Yes. Volkswagen has started using Google's 20-qubit quantum computer (or possibly even the 49-qubit one, which will be announced this March): https://media.vw.com/releases/951 https://media.vw.com/releases/951 IBM is also giving select customers access to its real 17-qubit quantum computer.
- skykooler 9y ago
  What does a car manufacturer do with a quantum computer?
  - vtomole 9y ago
    Quantum computers can be used for some optimization problems.
jessriedel 9y ago
There are no commerically useful quantum computers yet. Asking whether there are "real" quantum computers is like asking whether 6 noisy transistors wired together in a lab in 1940s were a real (classical) computer.

obastani 9y ago

D-Wave is not a "real" quantum computer in the sense that it is not asymptotically faster than a classical computer. Quantum computers with very few Quibits have existed for a while -- I believe the current record is 17 quibits [1]. I believe that to factor an n-bit integer, you need roughly n bits. So right now, we can factor 17 bit integers, which isn't very useful yet. However, I have read that for quantum simulations, it 30 quibit quantum computers might already be useful. [1] https://en.wikipedia.org/wiki/Timeline_of_quantum_computing https://en.wikipedia.org/wiki/Timeline_of_quantum_computing

krastanov 9y ago
It is worse than that. To factor n bit number you need roughly n "logical" qubits, i.e. qubits that can store information almost indefinitely. The quantum computers that we have contain low quality "physical" qubits that lose their content after a few millisecond. You need to put an error correcting code on top of the physical qubits to encode the logical qubits. You can expect to need 100s or 1000s of physical qubits per logical qubit. I.e. to decode modern public key encryption you need a computer with millions of qubits. Today we have less than 50 in the best research hardware on the planet.
- gaze 9y ago
  Or a good cavity or two.
- marcosdumay 9y ago
  This one I don't get. Isn't "a few milliseconds" more than enough time to gather a guess on integer factorization (and most of the useful problems)? Wouldn't it suffice to run your program again and again over the same short-lived qubits?

mtgx 9y ago

Yes. Volkswagen has started using Google's 20-qubit quantum computer (or possibly even the 49-qubit one, which will be announced this March): https://media.vw.com/releases/951 https://media.vw.com/releases/951 IBM is also giving select customers access to its real 17-qubit quantum computer.

skykooler 9y ago
What does a car manufacturer do with a quantum computer?
- vtomole 9y ago
  Quantum computers can be used for some optimization problems.

jessriedel 9y ago

There are no commerically useful quantum computers yet. Asking whether there are "real" quantum computers is like asking whether 6 noisy transistors wired together in a lab in 1940s were a real (classical) computer.