
IBM Raises the Bar with a 50-Qubit Quantum Computer - okket
https://www.technologyreview.com/s/609451/ibm-raises-the-bar-with-a-50-qubit-quantum-computer/
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mtgx
I think they only announced an early version of their prototype, and it's not
clear if it's even implemented yet.

Google was supposed to announce their own 49-qubit quantum computer this year
- one that actually works - but it seems they haven't had time to finish it,
or maybe they weren't satisfied with its performance and didn't want to
overhype it.

Also, I think IBM proving that 56-qubits can be simulated wasn't a simulation
of a universal quantum computer, but a more specific simulation. The record in
universal quantum computer simulation seems to be 46-qubits:

[http://www.fz-
juelich.de/SharedDocs/Pressemitteilungen/UK/EN...](http://www.fz-
juelich.de/SharedDocs/Pressemitteilungen/UK/EN/2017/2017-12-15-world-record-
juelich-researchers-simulate-quantum-computer.html)

Also, interestingly enough, the number of qubits that can be simulated seems
to increase by 1 every 2 years. I suppose this is because generally you need
2x the memory for your supercomputer to add an extra qubit to the simulation.
Being able to double the memory every two years seems to make sense from
Moore's Law perspective.

In that case, we should be able to _simulate_ a 50-qubit quantum computer by
2025. So any real quantum computer that has 50 logical qubits and is built by
2025 should be able to prove quantum supremacy.

~~~
ineedasername
I'm familiar with the 56 qubit simulation from IBM: That does not appear to be
significantly restricted in any way, at least not based on the limited
understanding I can glean from their publication's results & conclusions (I'm
not a quantum computer scientist or physicist). They appear to have found a
practical tensor-based work around to the previous exponentially increasing
memory requirements.

Moreover it is one that can, in limited circumstances, be applied in a
paralellized, distributed environments (cloud). _That_ appears to be the
limitation: They successfully simulated a 56-qubit computer, but many some
workloads using their method cannot be distributed, and must be computed
within the same environment. I.e., they made two advancements: 1: A successful
simulation, and 2: it can be done distributively, only for certain workloads.

Of course it's all roughly a billion times slower than a true quantum
computer.

