Comment by ahelwer | Hacker News Reader

Comment by ahelwer | Hacker News Reader

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I'm legitimately excited by quantum computing. The field is moving SO much faster than popular knowledge, which seems to believe a quantum computer will arrive at the same time as a workable fusion reactor. Real quantum computers exist RIGHT NOW. You can even write a program and run it on one from IBM![0] Google and Microsoft are both dumping resources into creating commercially-available quantum computers. Google says it will demonstrate a quantum computer in mere months which outperforms a classical computer on some problem.[1] The real value of quantum computers is not found in breaking RSA. Simulated molecular dynamics sees an exponential speedup over classical methods; this has huge ramifications for drug & material design.[2] What a time to be alive!

I have a BSc in Computer Science, and am teaching myself quantum computing. I'm really liking the book Quantum Computer Science: An Introduction by David Mermin. All this stuff is within your grasp! You aren't required to understand quantum weirdness to use a quantum computer.

[0] https://quantumexperience.ng.bluemix.net/qx/experience

[1] https://www.technologyreview.com/s/609035/google-reveals-blu...

[2] https://www.chemistryworld.com/feature/quantum-chemistry-on-...

"Real quantum computers exist RIGHT NOW. You can even write a program and run it on one from IBM!"

Let's be a bit realistic. It's a 5 qubit processor. I'm not sure how excited the general population were when the first 5 bit processor was available. There is still a ways to go before actually useful quantum computers are generally available.

"You have access to one now with the Quantum Experience. It is small at the moment, with a five-qubit processor, but it is a work-in-progress that we are continually improving."[0]

[0] - https://quantumexperience.ng.bluemix.net/qx/tutorial?section...

Is that a legitimate analogy? My understanding is that the number of qbits of a quantum computer are not fairly compared to the number of classical bits needed in order to make a useful computation.

It's even more limiting. A 5 qubit computer can get the expected efficiency of a quantum algorithm that needs a working memory of less than 5 qubits. That's it. Furthermore, the scaling is entirely different - a 8 bit computer can simulate 16-bit calculations with a limited number of primitives - e.g. a 16-bit multiply can be made with four 8-bit multiplies; but the quantum operations don't stack that way; you have to "read" the values in between, collapsing all the quantum states.

So for quite a few algorithms there are no efficient ways to stretch the size limit, you're back to brute force. If you have a quantum computer that allows you to e.g. break a 128 bit keys, then factoring a 129 bit key takes twice as much time, a 130bit key takes four times as much, and a 256 bit key takes 2^128 times as much time.

At least they seemed pretty exited with Intel 4004.

Did they actually, outside of happy Busicom calculator users? Even 8008 "looked okay, but nobody used it" - http://ethw.org/Oral-History:Masatoshi_Shima

I guess I misread it.

I wanted to convey that there were some groups actually happy about it.

The comparison between qbits and classical bits is somewhat specious.

qbits allow up to twice as many 'states' per bit when compared to classical bits.[0]

As for the public excitement, that will depend on someone making something exiting with the x bits available.

[0]https://youtu.be/w5rCn593Dig

I wonder how to reconcile the apparently exciting stuff going on in quantum computing with a conversation I had with a Harvard quantum computing PhD last year (I know very little about the field myself, so I unfortunately can't comment much on specifics here—I just know the guy was legit because of other people I knew who worked with him): he said he'd chosen the wrong field 'cause it has basically played out that quantum computing is intrinsically more limited and less exciting than what people had hoped for, and that a lot of big companies were starting to realize they'd wasted tons of money on it. (This was admittedly all being stated in an exaggerated and joking style, but he did seem serious about the basic idea.) Has there been something in the last year that's changed things? Or maybe his opinion was just an outlier?

Edit: that could've been up to two years ago, thinking about it.

> this has huge ramifications for drug & material design

Is the realistically any chance that a significant part of that innovation will happen in startups / new companies, or will this mostly play out in existing pharma/chemistry industry giants?

I read a news announcement on, I believe, IEEE, that Intel had gotten a manufacturing process down for a 17-qubit chip and had shipped it to their research lab in the Netherlands. There are certainly developments left and right. It will be interesting to see where quantum computing ends up... I could certainly see big possibilities for it in the communications sphere, guaranteeing link integrity and things like that.

Your comment made me wonder: would quantum computing help with simulating plasma dynamics in a way that would help us improve fusion reactors?

No, plasma physics is one of the few areas of modern physics in which quantum mechanics is not relevant: https://www.reddit.com/r/AskPhysics/comments/3nohxy/plasma_p...

Well that's a bummer.

Almost certainly not. The quantum computer is useful to get around the exponential scaling of problem difficulty in simulating quantum systems. In plasma physics that's not the issue. It's the crazy large size of the problem that scales in a classical and otherwise reasonable manner.

I also strongly recommend 'Quantum Computing for Computer Scientists'...this is a really, really good book for those coming from a C.S. background.

I totally agree. It lays out the minimum of the physics and mathematics background needed to get into it as a computer scientist.

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