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

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.

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.