The Possible Effects of Quantum Computing

craigj0 asks: "When quantum computers become more possible it will destroy our current encyption schemes but create a new type. My question is will it destroy non-factoring based encryption? And if it does what will the world be like during the transition stage from classic computers to quantum computers? How will the internet work when not all people have quantum technology and still want their digital privacy? Perhaps quantum plugin devices may be used to create hybrid computers?" Interesting issue here: What futures does Slashdot forcast when Quantum Computing becomes a reality?

Comments

Ramblings on the Quantum ramifications

[Brecker]

It seems that if quantum computers ever become a reality (if they haven't already...), they will be the toys of nuclear powers and their favorite universities for quite a while--like the bomb and Berkeley. After a bit, large corporations will be able to afford the technology, and a few will find uses that warrant the tremendous cost. There will be an effort from day one to bring the technology to the home user, but quantum physics are pretty out there, and the devices will be doubtless very hard to miniaturize.

So, most of us will be forced to use RSA, even when we know the the echelon system can crack our 4096-bit export-restricted keys in all of 2.3 ns (give or take a few orders of magnitude).

This will lead privacy-concerned Americans to do what is becoming popular in countries where strong crypto is illegal: we will turn to steganography. For those slashdotters who haven't read Simon Singh and aren't up on their cryptic (no pun intended) english, that's the art of hiding messages. We sometimes call it security through obscurity. We all know that it's not really no security. If I'm correct, it'll be the best security available to us.

I actually got to ask Simon Singh this question at a recent book reading, and his reply was quite interesting. He pointed out that in addition to the inroads on personal privacy and financial security, the real danger might lie in the realm of world politics. He suggested that the presence of governments that basically posess information omnipotence could drastically alter the balances of world power that we currently have. We all know that the Allied crack of the German cryptosystem was crucial to our victory in WW2. International-conspiracy theorists/prophets should have a field day with the possibilities.

Factorisation of Very Large values

[DaveHowe]

Hmmm. I doubt we will see a major advance in quantum code-breaking in the next (say) twenty years.
It has taken years of research just to build a two or three bit machine, and increasing a RSA or DH key by just a few bits would require doubling the number of "parallel universe computing cells" that are required to crack it. I can't see massive, secret research on this being funded well enough - particularly as it is "cheaper" in most senses to use other methods to defeat keys (most of which require physical intrusion to the machine in question or subversion of trusted personnel, but that has always been a standard operating procedure).

At worst, I think we will see the minimum key sizes considered secure increase, maybe by an order of magnitude, but without a change to the fundamental schemes in use - after all, with QC we are talking faster application of existing techniques, not a entirely new field.
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The true effects of quantum computers

[HyLander42]

First, I'd like to point out that quantum computation and quantum encryption are two almost completely separate concepts. Quantum encryption is based on the fact that quantum states cannot be measured without altering. The most common example is the polarization of a photon, but it will work for any quantum state, so long as there exist, effectively, two unique states that can transmit the data.

Quantum computation, however, is much more complex and much more interesting. Quantum computers are based on the concept of quantum entanglement, the ability of a quantum state to exist in a superposition of all of its mutually exclusive states: It's a 1 and a 0. However, this is not as easy to use as one might think. While it's true that if you have n quantum logic gates you have the ability to input 2^n data values simultaneously (as opposed to only 1 piece of data if you have n digital logic gates), this is not going to be the end of classical computing for a few reasons. First, quantum computers have to be perfectly reversible. That means for every output there's an input and vice versa. And there has to be no way of knowing the initial states of the data. You don't process data, you process probabilities in a quantum computer; if you know exactly what any one value is throughout the computation, you can find out all of the values: the superposition ends and you're stuck with a useless chunk of machinery. This means YOU CAN ONLY GET ONE RESULT FROM ANY QUANTUM COMPUTATION, THE END RESULT. You can't see what the data in the middle is or the computer becomes useless. (Landauer's principle makes heat loss data loss. When your processor gets hot, it's losing data. If the same thing happened to a quantum computer, it wouldn't be quantum anymore.) Decoherence is what happens when you randomly lose data to the environment by design, not by choice, and the superposition ends. This is bad for Q.C. Oh, and quantum computers can only do *some* things faster, like prime factorization and discrete logarithms. Not multiplication or addition. Plus, the circuits that would do basic arithmetic would be bigger and slower than what you've currently got.

So what does this all mean? It means that quantum computers are going to provide some advantages (real quick big number factorization), and some disadvantages (that whole RSA standard). The most realistic initial use of quantum computers will be as add-ons to existing super-computers to resolve certain types of NP-Complete headaches that regular math can't simplify yet. At best they will someday be an add-on to your PC; but they will never replace the digital computer.

- HyLander

If you want more info, check out http://www.qubit.org, it's got some decent tutorials, or email me at hylander42@hotmail.com.

Doesn't Matter

[devphil]

How the computer operates is beside the point. The people who use them are still going to be assholes to the people who keep them running. So it sucks in quantum amounts; it still sucks. So we'll have "F1rst QuAnTuM P0st!" articles instead. Spam will come in multiple flavors: up, down, strange, charm...

All hardware sucks. All software sucks. Everybody is considered a jerk by somebody. Lusers get LARTed, BOFHs get drunk. The sun rises, the sun sets, the Sun crashes. It is the way of things.


-A Sysadmin Having a Bad Day