It should also be noted that not every kind of computational problem can be solved efficiently using quantum computers.
It's even been shown that for certain classes of problems, *emulating* quantum computing on a regular processor is faster.
As with most things - it's not an either/or situation, it's an also/and situation. Current technology (or some future analogy of it) will be with us for a LONG time.
Quantum computers really aren't fundamentally much better at solving the problems your computer spends the vast majority of its time working on. Without getting into a discussion of computational complexity theory, where quantum computers really shine is in a class of problems called Nondeterministic Polynomial time (NP). Basically, these are problems where the only possible way to solve them in an ordinary computer is to check every possible answer one by one until you find one that fits.
Ordinary computers solve problems by breaking them down into tiny pieces and working on each piece one at a time. There is no problem they can't solve given enough time- bigger, harder problems just get turned into more pieces and take more time to finish.
Quantum computers, on the other hand, work best when you don't break down the problems. If you have a computer with enough qubits to describe the entire problem, then it can check every possible answer at the same time. This only works if the computer has enough qubits for the entire problem, but its a lot faster than trying each answer one-by-one.
For NP problems, this can mean the difference between being done in an instant versus waiting a few billion years. But for most problems, there are much better ways to solve them with ordinary computers, and quantum computers don't really offer a lot of advantage.
I expect when quantum computers start getting into the hundreds of reliable qubits, the government will take up an intense interest in the research and keeping it away from everybody else. Many billions will be spent so that the NSA can easily break everybody's codes, and nobody else can. Codebreaking is really the only obvious application for quantum computers under 100K qubits. After that breaks down and we get into the millions of qubits, certain major corporations will start getting one or two- Google for search algorithms, UPS for route planning (no, really), etc. Maybe someday (not in the next 25 years) we'll see them as secondary processors (a QPU?). I doubt if they will ever primary means of computation, though. For non-NP problems, they're just not worth the trouble.
@XandraMuses: Nicely explained, as NP problems are everywhere. For those who don't understand, NP problems are ones that can't be described by a polynomial time relation, such as x^2 + 3x + 1. They deal more with permutations and combinations. For example, say you have to assign 300 students to 300 lockers with stipulating conditions such as certain students can't be by each other, some must be in a certain number range, etc. The only way computers can solve these is by guessing and checking, there's no efficient way to do it, and moreover, guaranteeing an optimal solution is even worse.
Exciting stuff. I've understood for a long time that quantum computing is going to radically change if not destroy public key encryption, which of course would render all internet SSL security null and void and bring internet commerce to a screeching halt.
I wonder if they increased the bit size of the keys in public key encryption enough, would it eventually be able to stave off attempts to crack it using quantum computing?
That means that no cloud data we would keep would be safe! Or not?
Or is it that by the time the "code breaking" get quantum, the code protecting will too?
@stryder100: Wait a minute, let's say you have an ordinary computer, and you created an AES key on it. It would take a supercomputer quite a few BILLION years to crack it. source: [www.nist.gov] So that if you have a quantum computer, you can create even more secure encryption types that would take even a quantum computer even longer to crack. the only possible danger is if someone secretly develops a quantum computer and uses it to hack into things.
@TheAlmeida: I'd tend to think that steady escalation is how it would go. You know, given that mankind has developed all kinds of new technologies in our existence, and we haven't shattered our whole society yet.
I suppose the fact that it takes dozens of years to develop this kind of stuff helps. Sure, someone drops a functioning quantum computer designed for brute-force hacking into 2009, sure, internet's dead. But since it takes a long time (and a lot of people) to develop, you get people who build better ways to defend against malicious attackers as the attacks themselves are developed.
@stryder100: If I recall correctly from a brief crypto course I took years ago, public key encryption works basically by generating a public key that is based on the product of two very large randomly selected prime numbers. The encryption algorithm is a one-way algorithm if you only know the public key; you need to know the prime factors that the public key is based on to reverse it. The owner of the key knows the two primes he or she used to make the public key, so can decrypt messages encrypted with his or her public key. What makes this method of encryption secure is the fact that there's no good way to factor a large number- you have to see if it's a multiple of 2, then if it's a multiple of 3, then 5, etc. There are no tricks to make it go faster. With a key made from two really huge prime factors, this process is too slow to work.
As I understand it, a quantum computer's parallel processing makes factoring much faster. Instead of trying each factor one at a time, you can try them all simultaneously through the magic of superposition, so factoring a large number becomes trivial. Even if you have a really big key, a quantum computer with sufficient qbits can break it really quickly just based on the way it factors numbers compared to a standard processor.
Hopefully by the time those kinds of quantum computers roll around we'll have gotten quantum cryptography working, which is 100% unbreakable due to the laws of physics.
Quantum mechanics is logically flawed in the first place. Especially the way the Schrodinger's cat experiment is interpreted. I dont see how we will be able to make computers with a good logics system.
@FlameCell: Most people fail to realize that Schrodinger's cat was an illustration of how ludicrous it is to apply quantum theory to actual reality. Tragically, it is usually misinterpreted as exactly the opposite.
@Gann: "Schrodinger's cat was an illustration of how ludicrous it is to apply quantum theory to actual reality." Really? I thought it was a thought experiment used to demonstrate entanglement and superposition on a 'macro' scale.
As for the OP's comment about quantum mechanics being "logically flawed," um, what? How so? And why exactly do you think quantum computing wouldn't provide a "good logics system"? There are certainly some issues, but assuming they can be worked out, qubits will replace bits in our lifetime.
Actually it seems not to be that far away. You see, today's tech uses digital circuits, meaning that they manipulate data in terms of ones and zeroes. Quantum computing is actually talking about computers that can compute on an _analog_ level.
This may sound backward but it actually is far better since a datum ( a bit in digital circuits ) can hold MORE than two values. This allows you to hold more data, process more data, and do it faster. As of this moment, there is one basic electronic component that can do this. It is the memristor. [en.wikipedia.org] This magical little component can 'store' the last voltage that was passed through it. It therefore can be described as the beginning of analog computing.
But then we have a problem. Since analog data is not discrete ( clearly defined states ) there will have to be some sort of solution for measuring it.
@iSmithx_has_code_fu: Quantum computing is still discrete; it's just that it has more states than 2. I think it makes more sense to use quantum computing on neural networks which deals with nodes of multiple states.
@iSmithx_has_code_fu: Analog computers predated digital ones. The beauty of a digital system, and what makes it infinitely more practical, is its ability to tolerate noise. We trade off compactness for the ability to tolerate error. As ripfire states, quantum computing will be no different since the states are still very much discreet.
I've felt for a while that being technically inclined and experimental in how I deal with technology, I might, when my time comes, avoid the "dumb old person" stereotype, might actually be able to keep up.
It's crap like this that spoils my dream.
Ah, well. *grumble* Crazy flying kids, with their qPods. *mumble, grumble* Quit floating above my lawn.
@OCEntertainment: Ignoring the quantum mechanics part. The superposition principle is actually pretty easy to understand.
Superposition states that for systems with multiple inputs (A,B,C) you can evaluate there effect on the output (D) separately. So to find D, you set B and C to 0 and just figure out what A does... then you repeat this process.
The goofy thing is that a quantum bit occupies all states, which means that you solve for D just by evaluating it. Because D is the sum of all effects A, B, and C, and since they are quantum bits when you read the result, it has the all the solutions to whatever the input was.
@Kaiser-Machead:
Pinky:
- "Gee Brain, what do you want to do tonight?"
The Brain:
- "The same thing we do every night, Pinky—try to take over the world!
@Topsy_Elephante: Have you ever read any other "giz explains" before? Because they are all this awesome, and some are actually better than this since they actually go deeper into the subject. If you haven't I suggest you read them all. Btw, this wasn't meant to be smirky or smart in any way.
@geiko: I've read a few. I'm a history student, so physics and math are completely beyond me. For that reason, this one was enthralling. Just enough science for me to feel educated, but not enough for me to feel lost.
08/20/09
08/20/09
Oh yeah, and Crysis freezes.
08/20/09
08/19/09
It's even been shown that for certain classes of problems, *emulating* quantum computing on a regular processor is faster.
As with most things - it's not an either/or situation, it's an also/and situation. Current technology (or some future analogy of it) will be with us for a LONG time.
08/19/09
Ordinary computers solve problems by breaking them down into tiny pieces and working on each piece one at a time. There is no problem they can't solve given enough time- bigger, harder problems just get turned into more pieces and take more time to finish.
Quantum computers, on the other hand, work best when you don't break down the problems. If you have a computer with enough qubits to describe the entire problem, then it can check every possible answer at the same time. This only works if the computer has enough qubits for the entire problem, but its a lot faster than trying each answer one-by-one.
For NP problems, this can mean the difference between being done in an instant versus waiting a few billion years. But for most problems, there are much better ways to solve them with ordinary computers, and quantum computers don't really offer a lot of advantage.
I expect when quantum computers start getting into the hundreds of reliable qubits, the government will take up an intense interest in the research and keeping it away from everybody else. Many billions will be spent so that the NSA can easily break everybody's codes, and nobody else can. Codebreaking is really the only obvious application for quantum computers under 100K qubits. After that breaks down and we get into the millions of qubits, certain major corporations will start getting one or two- Google for search algorithms, UPS for route planning (no, really), etc. Maybe someday (not in the next 25 years) we'll see them as secondary processors (a QPU?). I doubt if they will ever primary means of computation, though. For non-NP problems, they're just not worth the trouble.
08/19/09
08/19/09
My cats are wondering why quantum physics is so predisposed to locking felines in boxes with uranium atoms and poison gas.
08/19/09
i wonder if his cat survived, who could stand the curiosity of not knowing if his cat was alive or dead...
08/19/09
08/19/09
08/19/09
08/19/09
08/19/09
08/19/09
I understood it as our current computers being powered by one dead cat and quantum computers being powered by two live cats.
08/19/09
Now, if you leave one cat in the box, then eventually it'll die of starvation; what happens to the cat you set free?
08/19/09
I wonder if they increased the bit size of the keys in public key encryption enough, would it eventually be able to stave off attempts to crack it using quantum computing?
Enquiring minds want to know.
08/19/09
That means that no cloud data we would keep would be safe! Or not?
Or is it that by the time the "code breaking" get quantum, the code protecting will too?
08/19/09
08/19/09
I suppose the fact that it takes dozens of years to develop this kind of stuff helps. Sure, someone drops a functioning quantum computer designed for brute-force hacking into 2009, sure, internet's dead. But since it takes a long time (and a lot of people) to develop, you get people who build better ways to defend against malicious attackers as the attacks themselves are developed.
Crack WEP, someone makes WPA. It's a cycle.
08/19/09
As I understand it, a quantum computer's parallel processing makes factoring much faster. Instead of trying each factor one at a time, you can try them all simultaneously through the magic of superposition, so factoring a large number becomes trivial. Even if you have a really big key, a quantum computer with sufficient qbits can break it really quickly just based on the way it factors numbers compared to a standard processor.
Hopefully by the time those kinds of quantum computers roll around we'll have gotten quantum cryptography working, which is 100% unbreakable due to the laws of physics.
08/19/09
08/19/09
08/19/09
As for the OP's comment about quantum mechanics being "logically flawed," um, what? How so? And why exactly do you think quantum computing wouldn't provide a "good logics system"? There are certainly some issues, but assuming they can be worked out, qubits will replace bits in our lifetime.
08/19/09
This may sound backward but it actually is far better since a datum ( a bit in digital circuits ) can hold MORE than two values. This allows you to hold more data, process more data, and do it faster. As of this moment, there is one basic electronic component that can do this. It is the memristor. [en.wikipedia.org] This magical little component can 'store' the last voltage that was passed through it. It therefore can be described as the beginning of analog computing.
But then we have a problem. Since analog data is not discrete ( clearly defined states ) there will have to be some sort of solution for measuring it.
08/19/09
08/19/09
08/19/09
It's crap like this that spoils my dream.
Ah, well. *grumble* Crazy flying kids, with their qPods. *mumble, grumble* Quit floating above my lawn.
08/19/09
Superposition states that for systems with multiple inputs (A,B,C) you can evaluate there effect on the output (D) separately. So to find D, you set B and C to 0 and just figure out what A does... then you repeat this process.
The goofy thing is that a quantum bit occupies all states, which means that you solve for D just by evaluating it. Because D is the sum of all effects A, B, and C, and since they are quantum bits when you read the result, it has the all the solutions to whatever the input was.
Or magic... take your pick.
08/19/09
08/19/09
[www.voodish.co.uk]
Wanna enslave all humans, Mr. Jangles?
08/19/09
Pinky:
- "Gee Brain, what do you want to do tonight?"
The Brain:
- "The same thing we do every night, Pinky—try to take over the world!
08/19/09
08/19/09
08/19/09
08/19/09
08/19/09