What is Quantum computer. i can't get right idea

[faslan]

i searched about it and saw video but i can't get right idea

what is the advantage of Quantum computer than normal computer

[Endy0816]

Potentially allows for smaller chips, ternary system and reversible computing. Translates into something smaller, faster and more energy efficient.

 

Just to be clear, there a number of different methodologies being attempted at present.

 

Edit: Removed part about quarks, not sure what I was looking at there. Too easy for net malarkey to find a home in my brain :/

Edited March 14, 2014 by Endy0816

[imatfaal]

i searched about it and saw video but i can't get right idea

what is the advantage of Quantum computer than normal computer

Quantum computers are different from actual computer in the fundamental way in which they represent and manipulate data. NOTE - we have only just started on the path to quantum computing and thus most of the discussion is purely theoretical.

 

Quantum Computers do not use the bit (which is a digital on/off signal) they use a qubit. The qubit is a quantum superposition of states - these can be on and off together and a mixture of many states. When measured the qubit collapses to a digital state and in an experimental scenario gives an answer in terms of the proportion of 1s and 0s that correlate with the probability state of the qubit.

 

What is special about quantum computing is that quantum superpositions are not simple defined inputs - and with clever use of quantum uniform operators you can get quantum computers to seem to act upon every possible configuration all at the same time. Shor's algorithm shows how given a relatively simple quantum computer that integer factorization becomes markedly simpler - I think from polynomial time to logarithmic or some such nonsense; Shor's algorithm, or a modernisation, has actually be run on a real world quantum computer but it was only 8 qubit I think which is the sort of sums you can do in your head.

 

Quarks are smaller than electrons and can exist in more states than electrons. Potentially allows for smaller chips, ternary system and reversible computing. Translates into something smaller, faster and more energy efficient.

 

Just to be clear, there a number of different methodologies being attempted at present.

This is not quantum computing - we cannot even envisage free quarks at present. A free quark requires so much energy to pull it away from companions that another (anti) quark can be called into existence.

 

http://en.wikipedia.org/wiki/Color_confinement

[Delta1212]

 

Quantum computers are different from actual computer in the fundamental way in which they represent and manipulate data. NOTE - we have only just started on the path to quantum computing and thus most of the discussion is purely theoretical.

 

Quantum Computers do not use the bit (which is a digital on/off signal) they use a qubit. The qubit is a quantum superposition of states - these can be on and off together and a mixture of many states. When measured the qubit collapses to a digital state and in an experimental scenario gives an answer in terms of the proportion of 1s and 0s that correlate with the probability state of the qubit.

 

What is special about quantum computing is that quantum superpositions are not simple defined inputs - and with clever use of quantum uniform operators you can get quantum computers to seem to act upon every possible configuration all at the same time. Shor's algorithm shows how given a relatively simple quantum computer that integer factorization becomes markedly simpler - I think from polynomial time to logarithmic or some such nonsense; Shor's algorithm, or a modernisation, has actually be run on a real world quantum computer but it was only 8 qubit I think which is the sort of sums you can do in your head.

 

 

This is not quantum computing - we cannot even envisage free quarks at present. A free quark requires so much energy to pull it away from companions that another (anti) quark can be called into existence.

 

http://en.wikipedia.org/wiki/Color_confinement

I believe it brings factorization down to polynomial time rather than from polynomial time.

[imatfaal]

I believe it brings factorization down to polynomial time rather than from polynomial time.

I never could get big O notation and all that stuff. I think you are probably correct - is it exponential time down to polynomial?

Delta1212 - yep you were right . It has gone from exponential to polynomial (logarithmic)

 

[latex]O(2^{\sqrt[3]{n}})[/latex] to [latex] O(n log n)[/latex]

[Marshalscienceguy]

i searched about it and saw video but i can't get right idea

what is the advantage of Quantum computer than normal computer

Its a computer that goes twice as fast as a normal computer. A computer operates using sequences of 0 and 1. With a quantum computer you have 2 going at the same time so you can perform the task much quicker at the same speed. Its like saying one person can make 10 reports in an hour but you want it to go faster. So you get 2 people and finish it in half the time. A quantum computer also uses quantum bits.

[alkis3]

computer

a=2+2 -> b=3+5 -> c=10*4 -> d=6/2

 

quantum computer

a=2+2

b=3+5

c=10*4

d=6/2

----------1-----------2-----------3----------4--------5----------6------------> time

 

 

could be wrong.....

Edited April 3, 2014 by alkis3

[Greg H.]

Its a computer that goes twice as fast as a normal computer. A computer operates using sequences of 0 and 1. With a quantum computer you have 2 going at the same time so you can perform the task much quicker at the same speed. Its like saying one person can make 10 reports in an hour but you want it to go faster. So you get 2 people and finish it in half the time. A quantum computer also uses quantum bits.

A quantum computer is significantly faster than twice as fast as a normal computer. Try an order of magnitude faster or better.

[alkis3]

 

Religion is about belief regardless of the facts and science is about the facts regardless of belief.

as I know it is not

there is such effects as quantum erasure

also, the behavior of the electron depends on whether we look at it or not

 

the world in which we live stranger than we imagine......

Edited April 3, 2014 by alkis3

[Intellectual]

A normal computer uses 'bits' witch can be a one or a zero at a given moment, so they can only check off computational pathways one at a time, granted it is extremely fast comparative to a humans ability to think up several scenarios however this is still a limitation.

 

Quantum computers use quantum principles that an atom can be in several states at one time unless directly observed. Quantum Computing uses Qbits which can be both a one and a zero simultaneously and thus is able to process several problems at once increasing computational power 100 fold. The problem is if we are looking at the data, the state will stick and the data will become unreadable, scientists are currently looking to use quantum computing with indirect observation so data can be seen.

 

Quantum computers are theoretically so powerful they can predict natural disasters.

[imatfaal]

A normal computer uses 'bits' witch can be a one or a zero at a given moment, so they can only check off computational pathways one at a time, granted it is extremely fast comparative to a humans ability to think up several scenarios however this is still a limitation.

 

Quantum computers use quantum principles that an atom can be in several states at one time unless directly observed. Quantum Computing uses Qbits which can be both a one and a zero simultaneously and thus is able to process several problems at once increasing computational power 100 fold. The problem is if we are looking at the data, the state will stick and the data will become unreadable, scientists are currently looking to use quantum computing with indirect observation so data can be seen.

 

Quantum computers are theoretically so powerful they can predict natural disasters.

Ok the first bit is fine - except it is much more than one hundred-fold; you can represent all the states of a set of variable at once only limited by your register size. But the section regarding reading data is not what I have learnt - measurement and the necessary collapse of the superposition of the state into a certain position is all part of quantum computation. The trick is setting up the superposition and the unitary transformations of that superposition such that measurement does not further cloud your answer - but rather that from the myriad possibilities a smaller number (easily checkable) is returned.

 

And the bit about natural disasters seems like sci-fi to me

[Greg H.]

Quantum computers are theoretically so powerful they can predict natural disasters.

I don't know about that, but they will render modern encryption standards obsolete.

[Intellectual]

Ok the first bit is fine - except it is much more than one hundred-fold; you can represent all the states of a set of variable at once only limited by your register size. But the section regarding reading data is not what I have learnt - measurement and the necessary collapse of the superposition of the state into a certain position is all part of quantum computation. The trick is setting up the superposition and the unitary transformations of that superposition such that measurement does not further cloud your answer - but rather that from the myriad possibilities a smaller number (easily checkable) is returned.

 

And the bit about natural disasters seems like sci-fi to me

I realize this, I was just putting it in lamens terms

 

I don't know about that, but they will render modern encryption standards obsolete.

I read it somewhere

[Delta1212]

I realize this, I was just putting it in lamens terms

 

I read it somewhere

There is a lot of misinformation about quantum computing on the Internet. It's main advantage over a regular computer is not that it is inherently more powerful, there are just certain types of problems that it is better suited to handling. Predicting natural disasters is not one of those problems.

[imatfaal]

There is a lot of misinformation about quantum computing on the Internet. It's main advantage over a regular computer is not that it is inherently more powerful, there are just certain types of problems that it is better suited to handling. Predicting natural disasters is not one of those problems.

 

I would disagree with that Delta; the ability to perform unitary transformations on superpositions representing all possibilities in one go rather than one after the other is "inherently more powerful". It is for this unique ability that we continue to research them - I admit that in many situation this might not be a game-changer but it is much more than a marginal advantage. Predicting natural disasters would seem to suffer from the problem of ridiculous sensitivity to initial conditions under iterative processes - so agree it would not be magically solved

[Megidolaon]

Its a computer that goes twice as fast as a normal computer. A computer operates using sequences of 0 and 1. With a quantum computer you have 2 going at the same time so you can perform the task much quicker at the same speed. Its like saying one person can make 10 reports in an hour but you want it to go faster. So you get 2 people and finish it in half the time. A quantum computer also uses quantum bits.

lolwut?

it's not 0 / 0.5 / 1 for qbits.

It's every single number bewtween 0 and 1 which in theory are infinite.

 

But the speed of a quantum computer is limited by measuring technology. There are a couple of them but so far they can barely compute basic addition.

Not sure how it exactly works but it comes down to current pcs using transistors that are on or off, limiting their computational abilities to the amount of 0s and 1s you can get on the cpu. We long since reached the limit of what you can dop with a single core, which is why new pcs in the last years don't come with simply more powerful single core cpus but multicore cpus, the transistors can't get any smaller and you can't pack more onto a single core or they start to interfere with each other (iirc it's actually quantum mechanics, Heisenberg's Uncertainty Principle, which is the reason for the interference).

WSith a quantum computer you only need a single atom, hell a single electron in theory because the potential computational ability is still infinite.

But of course this is limited by how many of its quantum states you can measure in what time, which is extremely limited at the moment.

[Dekan]

How is a Quantum computer programmed? I mean, what computer language is used to program it

In conventional computers, the programming languages rely on "predictability". For example, in BASIC, if you write

 

LET X = 1

 

Then you know X will always have a precise value, ie 1

 

But in a Quantum computer, wouldn't the value of X always waver "unpredictably" between 0.99999 and 1.00001.

So, if you were writing a BASIC program for a Quantum computer, you'd have to put:

 

LET X = 0.99999 ~1.000001.

 

That doesn't seem like it could give very precise answers.

Has anyone yet invented a programming language for Quantum computers?

Edited May 11, 2014 by Dekan

[imatfaal]

How is a Quantum computer programmed? I mean, what computer language is used to program it

In conventional computers, the programming languages rely on "predictability". For example, in BASIC, if you write

 

LET X = 1

 

Then you know X will always have a precise value, ie 1

 

But in a Quantum computer, wouldn't the value of X always waver "unpredictably" between 0.99999 and 1.00001.

So, if you were writing a BASIC program for a Quantum computer, you'd have to put:

 

LET X = 0.99999 ~1.000001.

 

That doesn't seem like it could give very precise answers.

Has anyone yet invented a programming language for Quantum computers?

 

It is even just as complex as that - you have, for instance, 8 qubits in superposition which will represent every potential super-position (rather than one of 256). So rather than try and quickly process a single instruction on a single 8 bit word you set up a complex set of instructions that operate once on a 8 qubit word. This will be a set of unitary transforms that manipulate the superposition without measurement, the gates used are not the same but they can be manipulated at present to create more complex unitary transforms. The programming side of it is a lot further advanced than the physical implementation. I believe that the quantum bit of Shor's Algorithm, which is quantum factorisation, has actually be run on an 8 qubit system. You don't get an answer out like clockwork - but the use of quantum computation like the quantum fourier transform will drastically reduce the time.

[Dekan]

Thanks imatfaal, but it doesn't really answer the question - what language are Quantum computers programmed in?

Or do the programmers not use a language, but just put the question into the computer, then wait while the qubits manipulate all possible answers, until the right one pops out.

 

Rather like, instead of looking up someone's phone number in a directory, you just dialled all possible numbers until the right person answered.

 

I'm sorry if that sounds superficial, but the more I read about this, the more I get the impression that no-one knows what's going on. Which is what we should expect from Quantum Theory, I suppose!

[Sensei]

We long since reached the limit of what you can dop with a single core, which is why new pcs in the last years don't come with simply more powerful single core cpus but multicore cpus, the transistors can't get any smaller and you can't pack more onto a single core or they start to interfere with each other (iirc it's actually quantum mechanics, Heisenberg's Uncertainty Principle, which is the reason for the interference).

 

Increasing core quantity is cheap and easy way to increase power of processor without bothering with smaller scale elements etc.

We certainly (and thankfully) didn't hit the limit of how small transistors and elements can be, yet.

Graphics cards are now coming with 2880 cores btw.

http://www.nvidia.co.uk/object/graphics_cards_buy_now_uk.html

CPU can go GFX card route too. But it should be done by changing architecture permanently, and limiting instruction set (which is quite obsolete, basing on Intel 8086 from 1978), which will simplify making core. So there will be possible to pack them together in larger quantity tightly.

This would make all currently Intel compiled software obsolete, so industry is trying to avoid it as long as they can.

[Delta1212]

Thanks imatfaal, but it doesn't really answer the question - what language are Quantum computers programmed in?

Or do the programmers not use a language, but just put the question into the computer, then wait while the qubits manipulate all possible answers, until the right one pops out.

 

Rather like, instead of looking up someone's phone number in a directory, you just dialled all possible numbers until the right person answered.

 

I'm sorry if that sounds superficial, but the more I read about this, the more I get the impression that no-one knows what's going on. Which is what we should expect from Quantum Theory, I suppose!

Asking what language a quantum computer would be programmed in is a bit like asking what language a newborn baby speaks.

 

Programming languages are created by people to make it easier to program computers: They let people write commands in a way that is easy for people to understand and then let the computer translate those commands into machine language.

 

Presumably quantum computers would be programmed in some version of existing languages that are modified to handle the way a quantum computer operates, or in totally new as-yet-undeveloped-languages that computer scientists of the future will develop for the purpose of more easily programming a quantum computer.

[imatfaal]

+1 Delta - that's what I meant to say.

 

Dekan

At present we are still at the state in which you sling together a set of gates; quantum computation ideas are at the stage of set up superposition, run it through a Hadamard transform gate, then a set of X gates, a few Z, and another Hadamard, then measure, and finally run some classical stuff on the measurement to get answer. This is on the level of a half-adder or such like in binary computers - there is no programming language; there are truth tables in binary and mathematical functions in quantum

[Greg H.]

+1 Delta - that's what I meant to say.

 

Dekan

At present we are still at the state in which you sling together a set of gates; quantum computation ideas are at the stage of set up superposition, run it through a Hadamard transform gate, then a set of X gates, a few Z, and another Hadamard, then measure, and finally run some classical stuff on the measurement to get answer. This is on the level of a half-adder or such like in binary computers - there is no programming language; there are truth tables in binary and mathematical functions in quantum

Or to put it another way, it's the quantum computer version of assembly where you have to move the bits around in the memory by hand and calculate the outcomes. There's no such thing as BASIC or C++ for quantum computing - yet.

[imatfaal]

Or to put it another way, it's the quantum computer version of assembly where you have to move the bits around in the memory by hand and calculate the outcomes. There's no such thing as BASIC or C++ for quantum computing - yet.

 

I am not sure there ever will be - I think we will have classical superstructures with small objects that perform single "black box" operations; ie an operating system will be able to access a quantum fourier transform (classical in and out).

 

By the time we have serious quantum computational power to go beyond above idea I think the idea of programming will be slightly passe; we will be talking more about training and even educating semi-intelligent systems

[Greg H.]

 

I am not sure there ever will be - I think we will have classical superstructures with small objects that perform single "black box" operations; ie an operating system will be able to access a quantum fourier transform (classical in and out).

That's entirely possible. A "chip", if you will pardon the simplification, that does the quantum calculation and returns the result to a more traditional computer infratructure for consumption. In fact, I expect that to be a lot more likely that entire computers running on quantum based technology.