Quantum computer leap

May 18, 2012
Quantum computer leap
Dr André Carvalho. Photo by Dr Tim Wetherell.

(Phys.org) -- The main technical difficulty in building a quantum computer could soon be the thing that makes it possible to build one, according to new research from The Australian National University.

Dr André Carvalho, from the ARC Centre for Quantum Computation and Communication Technology and the Research School of Physics and Engineering, part of the ANU College of Physical and Mathematical Sciences, worked with collaborators from Brazil and Spain to come up with a new proposal for quantum computers. In his research, Dr Carvalho showed that disturbance – or – that prevents a quantum computer from operating accurately could become the very thing that makes it work.

“Most people have experienced some kind of computer error in their life – a file that doesn’t open, a CD that can’t be read – but we have ways to correct them. We also know how to correct errors in a quantum computer but we need to keep the noise level really, really low to do that,” he said.

“That’s been a problem, because to build a quantum computer you have to go down to atomic scales and deal with microscopic systems, which are extremely sensitive to noise.”

Surprisingly, the researchers found that the solution was to add even more noise to the system.

“We found that with the additional noise you can actually perform all the steps of the computation, provided that you measure the system, keep a close eye on it and intervene,” Dr Carvalho said.

“Because we have no control on the outcomes of the measurement – they are totally random – if we just passively wait it would take an infinite amount of time to extract even a very simple computation.

“It’s like the idea that if you let a monkey type randomly on a typewriter, eventually a Shakespearean play could come out. In principle, that can happen, but it is so unlikely that you’d have to wait forever.

“However, imagine that whenever the monkey types the right character in a particular position, you protect that position, so that any other typing there will not affect the desired character. This is sort of what we do in our scheme. By choosing smart ways to detect the random events, we can drive the system to implement any desired computation in the system in a finite time.”

Dr Carvalho said quantum information processing has the potential to revolutionise the way we perform computation tasks.

“If a quantum computer existed now, we could solve problems that are exceptionally difficult on current computers, such as cracking codes underlying Internet transactions.”

The research has been published in the journal Physical Review Letters.

Explore further: Attack on classical cryptography system raises security questions

More information: Quantum Computing with Incoherent Resources and Quantum Jumps, Phys. Rev. Lett. 108, 170501 (2012) DOI:10.1103/PhysRevLett.108.170501

Abstract
Spontaneous emission and the inelastic scattering of photons are two natural processes usually associated with decoherence and the reduction in the capacity to process quantum information. Here we show that, when suitably detected, these photons are sufficient to build all the fundamental blocks needed to perform quantum computation in the emitting qubits while protecting them from deleterious dissipative effects. We exemplify this by showing how to efficiently prepare graph states for the implementation of measurement-based quantum computation.

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kevinrtrs
1.4 / 5 (16) May 18, 2012
If a quantum computer existed now, we could solve problems that are exceptionally difficult on current computers, such as cracking codes underlying Internet transactions.

Do I understand this correctly - they want to use quantum computers to break into people's private transactions, i.e. they want to hack?
harry555
5 / 5 (8) May 18, 2012
No. You don't understand correctly.
El_Nose
5 / 5 (2) May 18, 2012
and that would be a crack not a hack.
Moebius
1 / 5 (12) May 18, 2012
If you had an infinite number of monkey's pressing keys on a keyboard at random forever they would never produce even one page of Shakespear. First, letters symbols and spaces don't appear at random so a random process is unlikely to duplicate the non-random frequency of those things. The most common thing in almost any language is the space. Would a monkey hit the space bar regularly after 5 to 10 other keys? No. Would a monkey hit the E 100 times for every Z? Again no. So no random process would ever duplicate much more than a few words of a non-random language.
Deathclock
3.4 / 5 (17) May 18, 2012
If you had an infinite number of monkey's pressing keys on a keyboard at random forever they would never produce even one page of Shakespear.


False, I don't think you understand the concept of infinity. Over the course of an infinite time scale anything that can happen will happen.

Also, you spelled Shakespeare wrong.
SoylentGrin
5 / 5 (3) May 18, 2012
Do I understand this correctly - they want to use quantum computers to break into people's private transactions


Quantum computers can make transactions unbreakable, even by other quantum computers. Unfortunately, the downside of that is that current encryption methods will be completely obsolete. So, they're not really trying to break current encryption, they're trying to bring about the next generation.

Quantum computers can be used for much, much more than internet transactions as well. :)
kaasinees
2.5 / 5 (8) May 18, 2012

False, I don't think you understand the concept of infinity. Over the course of an infinite time scale anything that can happen will happen.

Also, you spelled Shakespeare wrong.

Yevgen
4.2 / 5 (5) May 18, 2012
If you had an infinite number of monkey's pressing keys on a keyboard at random forever they would never produce even one page of Shakespear.


False, I don't think you understand the concept of infinity. Over the course of an infinite time scale anything that can happen will happen.


Strictly speaking, even thing that can not happen, will happen,
although with limited probability. For example if probability of
a single event is zero (which can be expressed as p=1/inf), then probability that this event will happen at least
once after infinite number of tries N is:
P = 1-(1-p)^N
substitute p=1/inf = 1/N (since N is infinity in this case):
P = lim (1-(1-p/N)^N , N-->inf) = 1-exp(-1)~0.632120559...

This has implications to spontaneous creation of something out
of nothing, as nothing is not mathematically stable over infinite
number of tries...
Regards, Yevgen
Deathclock
2.5 / 5 (8) May 18, 2012
Interesting...
stealthc
1 / 5 (1) May 18, 2012
If a quantum computer existed now, we could solve problems that are exceptionally difficult on current computers, such as cracking codes underlying Internet transactions.

Do I understand this correctly - they want to use quantum computers to break into people's private transactions, i.e. they want to hack?

You are correct quantum computers are important so that your government can keep you safe from yourselves. LOL! This is totally the reason why. You beat me to posting that quote, I think this is a very revealing quote, be sure to tell people exactly what their goals are with this. It isn't just a super-calculator it is something that gives the elitists a huge edge over the people they mistakenly released weaker binary computing technology to.
Terriva
1 / 5 (1) May 18, 2012
and that would be a crack not a hack.
If you crack the password, you can hack the ban accounts.

The intrinsic fuzziness is the main trick of speed of quantum computers - you cannot beat the uncertainty principle, which already limits the computational power of classical computers in many aspects of CPU technology. So that the quantum computers can become considerably faster only when they remain more fuzzy and approximate than the classical computers. Which render quantum computers rather as a hype powered with job places generation, than the actual progress. The phrase "fast idiots" applies to them a way more, than for classical computers.
Lurker2358
1 / 5 (5) May 18, 2012
False, I don't think you understand the concept of infinity. Over the course of an infinite time scale anything that can happen will happen.


Definitely false.

That is a gamblers fallacy.

Even given an infinite number of tries, a possible event with a finite probability is definitely NOT guaranteed to ever happen.
Lurker2358
3 / 5 (2) May 18, 2012
Yevgen:

You are completely wrong.

A "Limit" and a "value" are not the same thing.

Zero does NOT equal 1/infinity, not in any possible universe.

1/infinity is an infinitesmal, which is a ridiculously small number, but it is NOT equal to zero.

If an event has zero probability then it is not even a possibility.
Noumenon
1 / 5 (2) May 18, 2012
If you had an infinite number of monkey's pressing keys on a keyboard at random forever they would never produce even one page of Shakespear. First, letters symbols and spaces don't appear at random so a random process is unlikely to duplicate the non-random frequency of those things. The most common thing in almost any language is the space. Would a monkey hit the space bar regularly after 5 to 10 other keys? No. Would a monkey hit the E 100 times for every Z? Again no. So no random process would ever duplicate much more than a few words of a non-random language.


Unlikely does not equate to zero probability.
There is a proof here,..

http://en.wikiped..._theorem
unassailable
not rated yet May 18, 2012
"If a quantum computer existed now"

I might be misinterpreting something on their website, but D-Wave is advertising they have multiple working quantum computers (D-Wave one) and is allowing a select group of developers to test on the system. Is this something that isn't well known?
Shabs42
5 / 5 (6) May 18, 2012
Definitely false.

That is a gamblers fallacy.

Even given an infinite number of tries, a possible event with a finite probability is definitely NOT guaranteed to ever happen.


Definitely false yourself. The gambler's fallacy is believing that something random (and fair) like a coin toss going one way many times in a row increases the odds that it will begin going the other way more often.

Those monkeys could pound away for a trillion years and not be any "closer" to hitting a page of Shakespeare; but they could also do it on day 3. The odds of it happening on day 2 or day 8,271,938,572,938,273,857 are the exact same.

Point being, if you roll a 20 billion sided die enough times, it will land on one eventually. After all, it has to land on SOMETHING each time.
Deathclock
3.4 / 5 (10) May 18, 2012
False, I don't think you understand the concept of infinity. Over the course of an infinite time scale anything that can happen will happen.


Definitely false.

That is a gamblers fallacy.

Even given an infinite number of tries, a possible event with a finite probability is definitely NOT guaranteed to ever happen.


No, you're wrong, and no, this is not the gamblers fallacy... want to try again?
deisik
3.7 / 5 (3) May 19, 2012
Zero does NOT equal 1/infinity, not in any possible universe


That is not quite so. It all depends on the number system used and is actually a matter of convention. Infinity is not a real number, so it does not follow the same rules as reals do. It has its own set and these rules are definied right along with infinity

So what you say may be true in some number systems, It may be false or make no sense at all in other
tkjtkj
3.7 / 5 (3) May 19, 2012
Re: Yevgen 's :
"a single event is zero (which can be expressed as p=1/inf), then probability that this event will happen at least
once after infinite number of tries N is:
P = 1-(1-p)^N "

You have, my friend, RE-defined 'zero' in order to support your case ..
I hope not all would agree with your contention. You see, Zero is zero. It is not defined properly by contending that it is 'one' divided by aNY quantity, whether or the quantity has a big-enough size .. These concepts have zero meaning .. ie, less than
1/"inf" .
;)
deisik
3.7 / 5 (3) May 19, 2012
Zero is zero. It is not defined properly by contending that it is 'one' divided by aNY quantity, whether or the quantity has a big-enough size .. These concepts have zero meaning .. ie, less than 1/"inf" .


You seem to miss the whole idea behind the notion of infinity. It is not a quantity of big-enough size to begin with, and yes, in the extended real number system, which is widely used in physics, a real number divided by infinity is strictly equal to zero
Deathclock
2.3 / 5 (6) May 19, 2012
Anything divided by infinity equals zero (other than infinity itself). Infinity has no size, that's where you're objection fails when you talk about "big enough size". No matter what "big enough size" you might choose infinity is INFINITELY larger.

.9 repeating equals 1
.6 repeating equals 2/3
.3 repeating equals 1/3

Do you want to argue about these too?
mexican92
5 / 5 (1) May 20, 2012
To Moebius:

You know what? I was rather bad in maths at school;-) But I think that PRL is a serious and professional paper, which checks every article before publication. So, if something in their work had the slightest "chance" to be wrong, the authors would just not be published... Game over!;-)
antialias_physorg
not rated yet May 21, 2012
You are correct quantum computers are important so that your government can keep you safe from yourselves.

But don't you want your bank to have a secure channel to you (and to other banks)? I'd rather not have people hacking my bank accunt.
but D-Wave is advertising they have multiple working quantum computers

It's not really certain whether what they have actually is a quantum computer.

As to infinities: That is a limit, not a number. You can use limits LIKE numbers in a lot of math (and physics) but you have to be careful that you stay with limits or numbers and not mix the two.

Example: Dividing 1 by a limit will give you a limit, not a number. (i.e. dividing 1 by infinit will not gove you zero, but a limit arbitrarily close to zero). Otherwise you'd run into trouble with the aleph notation for infinities.

Example: Aleph-naught numbers are less than aleph-one ones. Both are infinite. But 1 divided by an aleph naught is always greater than 1 divided by aleph one.
Deathclock
1 / 5 (1) May 21, 2012
So AA, if anything divided by infinity is not zero but, as you say, a limit approaching zero (or arbitrarily close to zero), then you would also have to apply that to .9 repeating... you would have to say that .9 repeating does not equal 1 but it approaches and comes arbitrarily close to 1...

This isn't true, .9 repeating equals 1, and this can be proven formally.
antialias_physorg
5 / 5 (1) May 21, 2012
.9 repeating

That isn't a number but a limit (limit of adding 9/10^n starting at n equals 1).
Like .3333.... (which is .9 (repeating) divided by 3) it has no exact representation on the number line.

For example: You can show that there is no arbitrarily small epsilon betwen 1 and .9 (repeating)

BUT: you can also show that The sum over 99/100^n is always larger than the sum over 9/10^n, and that therefore the limit over the former for n to infinity is always larger than the limit over the latter).

Limits are quirky that way.
deisik
not rated yet May 21, 2012
Example: Dividing 1 by a limit will give you a limit, not a number. (i.e. dividing 1 by infinit will not gove you zero, but a limit arbitrarily close to zero). Otherwise you'd run into trouble with the aleph notation for infinities


Nope. Something arbitrarily close to zero is not a limit, zero is a limit. What you say is just another way of calling infinity a real number. If it were so, you would have to deal with the fact that, say, 2/inf is more than 1/inf which would break definition of infinity as a limit since there would be many such limits (meaning in effect that it is not a limit) and its properties thereof (such as infinity plus constant is equal to infinity, etc)
Deathclock
1 / 5 (1) May 22, 2012
.9 repeating

That isn't a number but a limit (limit of adding 9/10^n starting at n equals 1).
Like .3333.... (which is .9 (repeating) divided by 3) it has no exact representation on the number line.


I was taught otherwise in undergrad math courses..

For what it's worth:
http://en.wikiped...0.999...

".9 repeating denotes a real number that can be shown to be the number one."

This doesn't say that it is a limit that approaches 1, it says that it IS 1, and that is what I was taught.
antialias_physorg
not rated yet May 22, 2012
2/inf is more than 1/inf which would break definition of infinity

There are infinities and then there are infinities - and they can have different sizes. For further reading on they types of inifinities in mathemaics I'd refer you to aleph numbers:
http://en.wikiped...h_number
deisik
not rated yet May 22, 2012
"The aleph numbers differ from the infinity commonly found in algebra and calculus"

I thought we were discussing real number infinities not aleph numbers, right?

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