IBM Raises the Bar with a 50-Qubit Quantum Computer (technologyreview.com)

IBM said on Friday it has created a prototype 50 qubit quantum computer as it further increases the pressure on Google in the battle to commercialize quantum computing technology. The company is also making a 20-qubit system available through its cloud computing platform, it said. From a report: The announcement does not mean quantum computing is ready for common use. The system IBM has developed is still extremely finicky and challenging to use, as are those being built by others. In both the 50- and the 20-qubit systems, the quantum state is preserved for 90 microseconds -- a record for the industry, but still an extremely short period of time. Nonetheless, 50 qubits is a significant landmark in progress toward practical quantum computers. Other systems built so far have had limited capabilities and could perform only calculations that could also be done on a conventional supercomputer. A 50-qubit machine can do things that are extremely difficult to simulate without quantum technology. Whereas normal computers store information as either a 1 or a 0, quantum computers exploit two phenomena -- entanglement and superposition -- to process information differently.

Comments

Imagine a Beowulf cluster of these?

[Anonymous Coward]

But can it run Linux?

Re:Imagine a Beowulf cluster of these?

[billybob2001]

Yes.

And No.

At the same time.

encryption

[Anonymous Coward]

One of the reasons the three letter agencies like to store even encrypted communication is that quantum computers will allow breaking encrypted data in ways that classical computers can't do in any practical sense. An example is Shor's Algorithm for factoring numbers, which runs efficiently in a practical amount of time on a quantum computer and could be used to break public key crypto. If they have saved the current encrypted text they can later break that when quantum computing hits.

Quantum computing is not quite there yet but it is coming up the well.

Re:encryption

[TechyImmigrant]

The practical defenses against the hypothesized quantum cryptopocalypse are:
Grover Issues:
A) Double the key size for symmetric algorithms, MACs
B) Double your hash sizes (you can finesse in which situations, but for practical purposes just double them all)

Shor Issues:
C) Use Hash based signatures for certificates.
D) Replace RSA, DH and ECDH with something else. Lattice crypto is a contender. Some with claim NTRU is fine, but it's not practical.

You shouldn't have been using DSA in the first place. So that's moot.

The dilemma is that the fix for asymmetric key crypto is not clear. Various lattice proposals have come along and been broken. RWLE is a PITA to implement (although that might be getting better soon with some stuff I've seen) and generally we don't know what it's going to be.

On the positive side, it's all BS. They will not build a quantum computer capable of breaking RSA any time soon. TFS makes is sound they they got from 2 bits to 50 bits and so 256 bits are only a short way off. This is grossly misrepresenting the situation. You can make some fragile qbits cohere but you can't do iterative logic on it., You can make a reliable, error corrected qbit, but you can't make reliable error corrected qubits into a memory on which you can perform the quantum logic needed to implement Shor's algorithm. These are the barriers to cross and as far as I can tell, they have remained unsolved for many years. Upping the number of non-ecc qbits doesn't move us towards breaking public key crypto.

I may or may not be proven wrong, but we will have the symmetric upgrades deployed in most new silicon pretty soon and the conference circuit will remain well attended while the lattice crypto work continues. So there will be lots more travel to nice places.

Re:encryption

[TechyImmigrant]

Really? Isn't this all textbook stuff, except maybe for my DSA snark? Well DSA is very fragile, so I'll keep on snarking.

Here's a common one: M.H. Devoret and R.J.Schoelkopf , Science, Vol 339, 2013.

This has a diagram with a little green arrow from the 3rd stage to the 4th of the 7 stages of development. Saying we're at stage 3 and getting from the 3rd to the 4th stage is the current problem. That was 2013. We're still waiting.We haven't got to stage 4 (logical memory with longer liftime than physical qubits) from stage 3 (QND measurements for error correction and control). Stage 4 through 7 are entirely unsolved.

For all the supposed major advances in quantum computers, by the metric that matters, we haven't moved in 5 years.
 

Awfully large.

[king neckbeard]

50 cubits is an awfully large computer, and why do Americans have to use such archaic units?

Getting closer to testing quantum supremacy

[JoshuaZ]

We're getting closer and closer to testing quantum supremacy- the hypothesis that quantum computers can practically solve problems that classical computers cannot do https://en.wikipedia.org/wiki/Quantum_supremacy. Note that this is a practical statement; anything a quantum computer can do, a classical computer can do, but with potentially exponential slowdown. This follows from the fact that BQP https://en.wikipedia.org/wiki/BQP the set of problems that a quantum computer can do in polynomial time is within is contained in PSPACE https://en.wikipedia.org/wiki/PSPACE the set of things that a classical computer can do with polynomial space (since polynomial space calculations live in EXPTIME, the set of things requiring exponential time, the result follows).

It is very likely that before we see genuinely useful quantum computing (e.g. for factoring large numbers or simulating complicated chemical systems) we'll have an answer to the quantum supremacy question. I suspect that it is more likely that we'll have an answer in terms of boson sampling before we have an answer involving a universal quantum computer.

Essentially, boson sampling works by just looking at the distribution of bosons (well for convenience, photons) as they go through very simple optical objects. Boson sampling has two major advantages: first, we know it is actually *hard* in a technical sense for a classical computer to do unless some conjectures that pretty close to everyone believes are false. In particular, Scott Aaronson and Alex Arkipov proved that if a classical computer can do boson sampling efficiently then the polynomial hierarchy will collapse https://www.scottaaronson.com/papers/optics.pdf. For those who aren't theoretical compsci people, the polynomial hierarchy not collapsing is a statement which is only marginally stronger than P!=NP and is very widely believed. This is in contrast for example with factoring large numbers where if it turned out that classical computers could efficiently factor the only major conjecture that would turn out to be false would just be the difficulty of factoring itself. Second, boson sampling is much easier in many respects than what IBM is trying to do which requires much fancier systems, supercooled qubits, careful protection from stray particles, careful preservation of entanglement and all sorts of other stuff. Still, what they are doing is important and very necessary if we're going to actually have practical quantum computers ever.

Re:Coherence

[JoshuaZ]

We sort of know already that that isn't the case, at least it isn't the case for generic states. We know that because we can construct Bose-Einstein condensates https://en.wikipedia.org/wiki/Bose%E2%80%93Einstein_condensate which are in a certain sense coherent states of lots of things together. That said, Gil Kalai has made more technical claims and conjectures which seem to follow from a similar intuition https://gilkalai.wordpress.com/2014/03/18/why-quantum-computers-cannot-work-the-movie/. Note that this isn't really like the thermodynamic situation of perpetual motion; there's no intrinsic law of physics that appears to be being violated by quantum computers, they just don't match our intuitions well.