The Quantum Computer

[Chaigidel]

if anyone is familiar with the theory of this machine please share--

from what I understand it could be the basis for computers with the ability to truly make information sorting , retrieval, and application an even more exponential process, and even lead to the birth of sentience among machines

some people even say our brains are a kind of quantum computer


will link an article as soon as I find one :O

[chris_uk_83]

Where a standard computer uses bits to store informations, that are either on or off, a quantum computer uses qubits (quantum bits) that can be either on, off or a superposition of both on and off simultaneously.

As yet, no quantum computer has been built, but I am reliably informed that up to 5 of these qubits have been linked together successfully. This link explains a little about qubits.

I'm not sure it'll make sentience any more likely in machines, but it will certainly improve processing power, since there are effectively now 3 states that each bit can be in rather than two.

Are our brains quantum computers? Maybe, I don't know enough about the brain. Fish might be your man here, but personally I doubt we, as a race, know enough about the brain to say one way or the other (it's pretty complicated you see )

[Hephaistos]

I doubt, that sentienent machines will be build in the next two or three centuries at least. And I do think sentience is not a question of the hardware but a combination of software and hardware.

A human for example is leaning over hears, until he has reached full mental capacity. In this time, his brain is building new neurals to be able to fully adapt to his expierences and to be able to learn and to solve problems, he has never heard of, on his own. A machine can't do that. if you don't say a computer how to solve a problem, he won't be able to solve it on its own. Ans as long, a computer isn't able to change its hardware hisself, everytime he need to, he can't learn. And not being able to learn means no sentience.

Of course quantum computers would be a real revolution: Quantums are moving with lightspeed, without producing heat and without the need of conductors. This would be incredible more effective.

[bubka]

As far as I knew, it consists of photons going through half-reflectors, so that they have a fifty percent probability of getting reflected. And here the quantum magic sets in, and the photon follows both the paths simultaneously, leading to a huge storage power. Hundred qubits store as much as two to the power of hundred bits. But this is purely theoretical. You can't actually ever attain it fully, but you can get a close approximation.

[numerosdecimus]

It depends on what "version" of a qubit(or quantum computer) you are talking about.

Fotonical computers may also be defined as quantum computers under certain criteria.

Is quantum computing possible? Yes and no. First of all it's almost all theoretical at the moment, but some first steps have been made, but these first steps are almost nothing comprred to what must be truly done if we are to have a qubit computer. Do you guys remember that experimental sucess in Austria? The one with the bridge? That's an example.

Why is it qubit processing so difficult? To put it simple, qubit processing brings a hole new level of difficulties concerning the measures necessary to maintain the processing method stable and actually funtional.

Here's some insight on things (I will keep things in a broad perspective, so some more speciffic details will be kept aside, and as such this can have some inaccuracies at a more detailed level)(I will also place some recent theories):

Why do we call our current technology "electronics", because it based on electrons. This technology requires method that can be defined at a macro/micro level. Even despite being micro, they still are perfectly reliable comercially as the probability of a critical error is extremely low.

However, qubit processing(quantum computers) do not relly not are controlled under these methods. When you talk about a quantum computer you're dealing with pure quantum mechanics and quantum control and this already is problem number one. According to the theory (and quantum reality) of complete impossibily of absolute quantum control there will always be "rebel reactions" coming from particle interaction, in other words there will always exist some degree of quantum impredictability and particles out of our control that will not behave according to our commands. This os not just a matter of having a few particles "rebelling particles" against the orders given to them, but they will also inevitably interact with all other particles in the system, thus creating "quantum interference". The only way completely eliminate all quantum "interference" is by putting the system in an absolute temperature of 0K, which is the equivalent of -273,15K. This measure speaking under absolute quantum terms, is completely impossible (however there are some theories, some says it's possible, others says it's not).

Take this example: you have 3 spaces. _ _ _ What combinations can you put(0 and 1), you can put 100, 010, 001, 110, 011, 111, 000, 101.

In a regular computer system you can only have available one of the combinations at a time, however in a quantum system you can have all of these combinations available at the same time because the system is composed of particles and their interaction, and each of these particles can be in a certain state (along with clusters of particles), so you can have all of these at the same time.

This kind of quantum computing is the one that is normally associated with the “science fiction” type, such as Stargate or Startrek, however, there are several types of quantum computers, and some are better than others, while others are more stable. Ironically some of these types of quantum computers aren’t that far from reality.

Currently(in my opinion), the single best chance we have of achieving quantum computing is through Photonics. Photonics uses photons instead of electrons. The advantage of this is that Photons are thousands of times lighter than Electrons, and as such you need less energy to transport them, however, the true advantage of photons is that they travel(in an atmosphere such as ours) at almost 300000KM/s. How does a photonic system work? The best way(still theoretical) would be to create a crystal like system, in which you use crystals to reflect and refract the light and these crystal would be less dense than aerogel, you can also have crystals composed by several crystals of different densities and the limits of the crystals would refract the light, in other words this one of the basis for “photon processing”. Another advantage is that you can make these crystals smaller and smaller, in other words you can have and entire endless system of nano crystals that would occupy an area equal the size of your thumb digit or even much small, another advantage is that this system could allow multi-processing, in other words it would be the equivalent of having several processors.

However, there is one HUGE disadvantage with this system so far, that until now it makes it completely impractical and that's the inexistence of an optical-transistor. How do you make a device that has the same function and behaviour of a normal transistor but instead it works with photons (light)? That’s why “pure photonics” may perhaps never be achievable, however, a mid term solution is already on the way and it will substitute our regular electronic technology in about 12 to 20 years, and that’s optical-electronics, this technology has its advantages and they are indeed quite many. Optical-electronics will allow computers to be approximately tens of times faster than our current computers, but even that technology has its theoretical limits, just like electronics has its.

Our brain is actually an electrical organic quantum computer that produces its electrical energy chemically, that’s the best definition I can find at the moment.

[ajm317]

My current research actually has potential applications in quantum computing. I also took a 1 quarter course on the subject. I have a copy of Neilson and Chaung (a quantum computing textbook) on my desk at my office.

There are a bunch of problems with quantum computers. I don't think you'll ever have one on your desk, however they don't need to become as widespread as current computers to be extremely useful.

The number 1 application they are currently recieving funding for is code breaking. In theory a quantum computer can factor numbers much more quickly than a classical computer can. Since modern encryption schemes are based on the idea that you can't factor large numbers in a reasonable time frame the first country to get a workable quantum computer will render all codes on the planet obsolete. They'll be able to read or see anything. E-mails, credit cards numbers etc.

On the flip side quantum computers also make it possible to transmit information COMPLETELY securely. If two quantum computers are talking it is possible for them to do so without anybody determining what they're saying.

Scientists are most interested in quantum computers because they hold the possibility to simulate complex quantum mechanical systems. This could lead to great breakthroughs in, for example, chemistry or biology.

In order to do quantum computing you need to construct something called a qubit, as others have mentioned. This is just the quantum equivalent of a bit. Because it's quantum it can be either up, down or in some mixture of the two. When you read a quantum bit that is in a superposition of two states it is entirely random which state you will get. For example, if a bit is in the state: sqrt(1/3)|1>+sqrt(2/3)|0> you have a 33% chance of measuring it to be 1, and a 66% chance of measuring it 0.

How can superposition be useful then? Well there are two ways.

1. You can construct your algorithms in such a clever way so that although superposition is used in intermediate states, your final qubit ends up either definately in 0 or definately in 1.
2. You can perform the calculation many times. This will allow you determine the coefficients of the superposition of states. This of course slows things down, but it can still do things much more quickly than a classical computer.

There are many possibilities for quantum bits, ranging from superconductors to photonic systems to what we're hoping to build in my lab, an array of atoms in optical traps. Nobody knows which one will end up being succesful, or even if any of them will be.

The biggest problem with quantum computing is something called decoherence. Decoherence is a measure of the time it takes your system to interact with the outside world. This is bad, because once it does so, the wave function of your qubit collapse, pretty much killing your computation. This is pretty much unavoidable. However, if you can make the decoherence time long enough and the computation time short enough you can still do useful calculations.

Most quantum computation schemes rely on something called entanglement to generate something called a 2 qubit gate. This is kind of complicated, but the gist of it is that when two particles are entangled (say two photons) what you measure on one determines what you would measure on another. Entanglement is a fascinating phenomena on its own, as it seems to transmit information quicker than the speed of light. This is how we get qubits to interact, which is vital if you want to make something more complex than a clock.

The current state of the art is a quantum computer that was able to factor the number 15. Unfortunately this system is not scaleable. In other words, it's never going to be able to do much better than that. It is impossible to predict when someone will make a useful quantum computer. It could 5 years from now, it could be 50, it could be 500.

There has been some discussion that the brain actually uses quantum computing, however at this time the majority opinion is that it probably does not.

[numerosdecimus]

My opinion that the brain was a quantum computer by nature was due to the fact that it used minerals as a "medium" in order to transfer the electrical impulses. It could be using indirectly some of the definitions that could qualify it as being a quantum computer.

What would be the best definition? Just calling it a electrical organic computer?

Now that I remember, another advantage of quantum computers will be for instance the capacity for extremely complex codification systems and parterns.

[ajm317]

My opinion that the brain was a quantum computer by nature was due to the fact that it used minerals as a "medium" in order to transfer the electrical impulses. It could be using indirectly some of the definitions that could qualify it as being a quantum computer.

What would be the best definition? Just calling it a electrical organic computer?

Well the distinguishing feature of a quantum computer is the qubit, a bit which can be in a superposition of states. Most people (but not all, notably Roger Penrose) believe the brain does not function this way. It's bits are classical bits, either 1 or 0, never both.

So I would term it as an organic classical computer.

[Chaigidel]

how many bytes does the human mind estimated contained like 4 terabytes?

[numerosdecimus]

how many bytes does the human mind estimated contained like 4 terabytes?

The human brain has a colossal amount of space, in other words, your "hard drive" won't have any space problems in the future.

Just don't forget to defragment it periodically! (ironically it seems that the brain does this automatically and indeed periodically).

Great, I just ruined my own joke...

[Gary88]

[Chaigidel]

yeah the sheer amount and difference in the information we process is amazing

the world becomes a very magical place when you begin to pick apart these various senses of course-- these sources of information

[Simetrical]

from what I understand it could be the basis for computers with the ability to truly make information sorting , retrieval, and application an even more exponential process, and even lead to the birth of sentience among machines

Nonsense. Quantum computers can execute certain algorithms faster than normal computers (or more precisely, more scalably, which is the important point). They might be able to execute algorithms that ordinary computers (Turing machines) can't at all, I don't know. They won't bring us any closer to sentience or anything like that, which needs not just much more power but much more programming.

however, the true advantage of photons is that they travel(in an atmosphere such as ours) at almost 300000KM/s.

That's of marginal importance. Currents in a typical (semi)conductor tend to travel at 10% or more of the speed of light, which is fast enough for most purposes. (The electrons themselves travel far slower, on the order of 100 micrometers per second, but that's not the important point.)

My opinion that the brain was a quantum computer by nature was due to the fact that it used minerals as a "medium" in order to transfer the electrical impulses. It could be using indirectly some of the definitions that could qualify it as being a quantum computer.

Quantum computers are those that directly make use of processes that do not classically exist. As far as we know, the brain's function can be explained 100% classically, and it is therefore not a quantum computer, probably. It's an electrochemical one.

how many bytes does the human mind estimated contained like 4 terabytes?

Depends how you measure it. It's not a wholly meaningful comparison. But 4 TB seems not too far from the first estimates from Google. It's close to being exceeded, in other words, by hard disk drives costing less than a hundred dollars (give it a couple more years).

[numerosdecimus]

Depends how you measure it. It's not a wholly meaningful comparison. But 4 TB seems not too far from the first estimates from Google. It's close to being exceeded, in other words, by hard disk drives costing less than a hundred dollars (give it a couple more years).

I don't have any certainties concerning this because I've seen almost endless different versions concerning this. It seems that the brain has a most efficient storaging methods and system in the sence that it seems that there no limit to the amount of information that can be stored in it( there would be a limit, but these space available is colossal, in my opinion it would be more than "just" 4TB). This is just my opinion according to what I've read so far.

[Simetrical]

As I said, the comparison isn't fully meaningful, because the brain cannot store arbitrary data, and the format of the data it does store is still basically unexplored, so it's not like you can move stuff back and forth between them. Until someone figures out a fully working brain-computer interface, it doesn't make much sense to talk about relative storage capacities.