Hacker News Reader

Comment by hamilyon2 | Hacker News Reader

The margin between 200 seconds and 2.5 days still exists

As far as I understand, the 2.5 days classical simulation gives you the total wavefunction, from which you can read the probability distribution. You only need to run it once. It's not clear to me whether the 200 seconds quantum computation is for getting (or rather sampling) the probability distribution, or for just one measurement. My point is, the classical simulation actually gives you much more data than the quantum computation -- you get the actual full probabilty distribution, not just an approximated sample of it (guess that's why IBM claims "higher fidelity").

I thought quantum supremacy was about having a quantum computer capable of doing more operations per second than any binary computer can do

Do you think it wouldn't be possible to simply upgrade the supercomputer to shave some time off those 2.5 days ?

To me it seems clear that everyone gullible already bought into the Cloud, ML/AI, CI/CD buzzwords and now they need a new buzzword to market.

That's not quantum supremacy. It's about doing something on a quantum computer that would be infeasible on a standard computer. This is because in some scenarios a single calculation by a quantum computer could be equivalent to a vast number (many trillions) of calculations made by a standard computer.

> more operations per second than any binary computer can do

> doing something on a quantum computer that would be infeasible on a standard computer

Sorry, but I fail to see how these two are different.

They use different "algorithms", so solving a problem can be done in very different ways for a quantum and a classical computer. Comparing the number of operations per second does not make sense because the advantage of quantum algorithms lies in the fact, that they can achieve the same results with (exponentially) fewer operations.

We can keep moving the goalposts and I can rephrase my claim to:

> it's a state when a quantum computer can achieve results that would require more operations on a binary computer than a binary computer has proven to be able to do

but the point will still stand.

We can't say we achieved quantum supremacy for this one thing because binary computers still have supremacy over everyting else.

I guess we can agree here that quantum supremacy was definitely not achieved since we are not clear on the definition of said quantum supremacy.

No, quantum supremacy is about quantum computers being better at one thing. Then there will be a reason to use them. It's like making a screwdriver when you already have a hammer. Sometime a hammer and nails is better and sometimes a screwdriver and screws is better. It's about picking the right tools for the job.

It isn't about them being better in the sense of faster than a classical computer, but rather scaling. Quantum computing is attractive because we expect that some operations scale much better with size on one compared to classical computing. ie if for a task the quantum algorithm is O(n) while the classical version is O(n!)

I think it's about running algorithms with big-O complexities lower than can be ran on a classical computer, not actually more ops.

Quantum supremacy is about scaling (big-O notation) - taking a classically O(2^N) problem and making it polynomial. The empirical experiments are just to show that the scaling works, and the uncertainty comes from the fact that we still can't fit very large N problems into current quantum computers. Effectively, they don't have enough RAM to even load the problem (i.e. enough available quantum states).

I think that’s where the

> and with far greater fidelity

comes into play.

A physical system will always be the fastest implementation of a computer simulating its own physics.

Some overhead is expected when using different hardware to simulate it.

What matters is asymptotic computational and memory complexity.

Yes but nobody cares.

The QC isn't cheap or available enough to be relevant is your can compute it reasonably well in a few days.

Reply on news.ycombinator.com