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Comment by dsp1234 | Hacker News Reader

"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...

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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

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