Fredkin Gate Breakthrough Brings Quantum Computing Within Closer Reach (pcworld.com)

An anonymous reader quotes a report from PCWorld: Quantum computers are based on atomic-scale quantum bits, or qubits, that can represent both 0 and 1 simultaneously. Realizing that potential, however, depends on the ability to build working quantum circuits. The quantum version of the classic Fredkin gate exchanges two qubits depending on the value of the third. It could be a key component of quantum circuitry, but because of the complexity involved, no one has ever managed to build one in the real world -- until now. Whereas the Fredkin gate typically requires a circuit of five logic operations, researchers from Griffith University and the University of Queensland used the quantum entanglement of particles of light to implement the controlled-SWAP operation directly. Essentially, the scientists demonstrated how to build large quantum circuits directly, without having to use numerous small logic gates. That, in turn, puts real quantum computers within closer reach.

Comments

Spooky confusion at a distance.

[Tablizer]

I give up, quantum stuff makes sorcery sound logical in comparison.

Too bad Einstein's not still around; maybe he could find a more down-to-earth or simpler explanation. He seemed to be the only prominent one questioning that something seems really out of whack, as if we are missing a yuuuuuge piece of the puzzle.

He solved the ether weirditity by plugging in relativity. Similarly, maybe the probability and multi/ghostiverses games will fade away when the equivalent of relativity is applied to quantum stuff.

Maybe particles are like sperm in that when one photon is apparently emitted, there's really many particles emitted, and the first one to hit (react) shuts off the other particles so that they are invisible, almost like neutrinos, so that we don't detect them.

Thus, the interference pattern really *is* a wave; it only looks like a lone particle upon detection because the others cloak. Well, I'm rambling, but you get the idea: there's a BIG IDEA out there to be discovered...

Re:Spooky confusion at a distance.

[Anonymous Coward]

The way I think about it now is that quantum computation is essentially multi-level logic, where we can actually do useful computations while staying in the multi-level domain.
The exact physics of the situation are irrelevant (unless you are a physicist trying to increase the number of qubits).

Re: Spooky confusion at a distance.

[Anonymous Coward]

The problem is that QM is straight forward if you have high school calculus plus some math, mostly notation, that would fit within a small appendix. Things like the particle wave duality aren't that mysterious or a problem at all if you can work out actual QM instead of trying to contemplate a bad analogy. A large amount of the mysticism and confusion is not there in what is a sophomore level class. Most of the problems people think make QM confusing comes from trying to make math-free analogies connecting to everyday experiences. This isn't unique to quantum, as you can make classical physics riddles that even physicists will get wrong using intuition, but can be worked out straightforwardly using a formal approach. This is not to say that there is a lack of questions still left even at the formal level, and there is always room for more simpler explanations. But like many things in life, you can't expect everything to be reducible to a level you can just skim through in a couple of minutes, and understanding some things in this world takes more dedication than half-assing. If you have some math background, even rusty, you can get through a couple chapters of an actual textbook instead of reading numerous popsci books.

Re: Spooky confusion at a distance.

[Tablizer]

But that's possibly like saying, "epicycles are straight forward to model if you remember your math". (Circular regression?) While possibly true, epicycles were the "wrong model" to begin with for orbital mechanics.

One can model just about any fake or spooky thing that follows patterns with math/algorithms, but that doesn't mean the model reflects the underlying mechanism well.

Re: Spooky confusion at a distance.

[Anonymous Coward]

No, it's actually the opposite. Epicycles are a complex mathematical model for a phenomenon that has a straightforward math-free analogy. The simple math-free explanation is "planets go around the sun, including Earth", or for "planets go around the Earth" for the epicycles explanation. The actual math of a two-body gravitational system in vacuum where one body is much heavier than the other is not that difficult, but it's more complicated than "planets go around the sun".

But people often say things like the guy below who talks about quantum computers pulling results from "the future", or the guy below that who constantly analogizes flocks of starlings, or thinking that the Many-Worlds interpretation implies that Sliders is possible, or they hear about observation making waveforms collapse and conclude that human beings, as the only conscious observers (maybe animals too), have mystical powers over reality. Deepak Chopra contributed to this. This is down to people extrapolating from oversimplified statements. But when you don't oversimplify, people don't understand at all. And if you show them numbers mixed with greek letters, they don't even try -- and I can hardly blame them; it's one thing to say that a painting sells for millions of dollars because it's a famous artist's work and all his art sells for a lot, and another to be told the entire sociopolitical context of the art world at the time and the particular history of that painting using terms-of-the-art I've maybe heard of but couldn't possibly define and probably couldn't even pronounce :).

That said, most high schools do not teach solving partial differential equations in their Calculus class. Schrodinger's equation is pretty critical. But you don't need to be an expert on PDEs to be able to pick up enough to verify and understand statements made be others; you'd just have trouble independently getting those insights.

Re: Spooky confusion at a distance.

[Anonymous Coward]

That said, most high schools do not teach solving partial differential equations in their Calculus class. Schrodinger's equation is pretty critical. But you don't need to be an expert on PDEs to be able to pick up enough to verify and understand statements made be others; you'd just have trouble independently getting those insights.

As is, many intro physics classes get by only covering some derivations, and spending more time on results (and often the QM ones just use hand waving arguments to get a rough form of the PDE solution that the students can confirm instead of spending a lot of time on PDEs more complicated than a particle in a well).

You probably don't even need calculus at all to get the formal gist of many things. Simply learning the concepts behind bra-ket notation, and glossing over the use of calculus to calculate actual values in more complicated cases, you can end up learning how to understand a lot of quantum computer and teleportation research using just algebra.

Re: Spooky confusion at a distance.

[dbIII]

You probably don't even need calculus at all to get the formal gist of many things

Only by learning via rote and parroting a list of rules. You need calculus to even work out what is going on with displacement, velocity and acceleration. Extremely easy calculus that makes more sense than looking at things any other way, but it's still calculus.

To start with it's a lot easier than the physics it's used to explain. What is so hard to understand about the area under a curve of a graph?

Re: Spooky confusion at a distance.

[Tablizer]

The problem with epicycles is they very quickly did not match data from observations, even with the attempts to nest epicycles within epicycles.

I'm not sure that's the case. I've never seen a proof that epicyces CANNOT be made to match observations within a reasonable observation time-frame. Whether they actually got them "good enough" in practice before Newton's work, I don't know. I'm mostly talking about potential.

Seeing how accurate nested epicycles COULD be would make an interesting research paper. (This is assuming the epicycles don't re-invent a sun-centered model.)

As somebody else mentioned, using an Earth-centric assumption was also part of the "problem" with the epicycle model, not just the usage of epicycles. But that doesn't change the general point. It was a model with (potentially?) sufficient predictive power, but didn't mirror the actual mechanism and system layout.

How does one know their model actually reflects the underlying mechanism, or is merely a fudging trick to produce a good-enough approximation?

(Incidentally, some say string theory is throwing dimensions at the problem similar to epicycles throwing nested circles at the problem. "Dimensional regression" of sorts.)

you can't just assume some simpler or easier theory exists.

That is indeed true. But QM models smell like kludges. That can be seen as an indicator that there may be a simpler explanation/model lurking out there to be discovered. Hunches are often the first step.

Re: Spooky confusion at a distance.

[Viol8]

"The problem is that QM is straight forward if you have high school calculus plus some math,"

You've obviously never heard Feynmans quote: "If you think you understand QM then you don't"

In fact no one understands the why, just the what. Giving the probabilities of what might happen in a QM system is one thing, asking WHY it happens in the first place or what a surposition really is, are still questions we're not even close to answering.

Re: Spooky confusion at a distance.

[shaitand]

Actually the heart of it seems to be very simple from a logical perspective. Our most complete and proven models are arithmetic and algebra, so many people use it to prove models but fail to realize arithmetic itself may well be the model. Arithmetic boils down to:

Where A is a number ranging from negative infinity to positive infinity which much include 1 and 0 regardless of base. Op represents an infinite number of potential logical operations and yet the results have a potential range that is identical to A. At this point A is not any specific number, it represents the entire range of values you can plug in there. Even reduced to the smallest base (2 or binary) the range must include 0, 1 and Infinity. This is the most raw and basic reality.

A op A = A

What can we determine from this model? Actually quite a bit.

1. In order to derive any information we must limit perspective, meaning reduce the infinite possibilities or collapse it to a discrete value but it must always follow the rules above since they are the rules of the universes "stuff."

2. Collapsing to either 0 or 1 requires the other as well as an infinite element. In other words as soon as an observer looks at the "stuff" through a limiting perspective you create not only the possibility of the "thing" which defines the limit but also the possibility of the things absence and the anti-thing which negates it thereby making that absence possible.

3. If you model reality as absolutely constrained in any fashion there will always be a window to higher and lower dimensions. This also means that patterning will emerge.

4. Information can be derived entangling things with other things. The information is paradoxically real and not real because infinite is the nature of "stuff."

A + A = 2A

There are quite a lot more. Especially when you think about yourself as an aware "thing" that is defining the constraints,

Re: Yawn

[Anonymous Coward]

Hakuna Ma Titties!

If it's anything like fusion...

[Sax Russell 5449D29A]

Quantum computing will always be 20 years away. Getting anything practical work done on quantum computers is not likely going to happen in our lifetimes (unless you redefine 'practical work', of course).

Re:If it's anything like fusion...

[JoshuaZ]

The primary reason that fusion has stayed far away has been a demonstrated lack of funding. See https://upload.wikimedia.org/wikipedia/commons/a/ab/U.S._historical_fusion_budget_vs._1976_ERDA_plan.png. Even given that, there's been by pretty much all major metrics steady improvement in fusion. See e.g. https://www.euronuclear.org/e-news/e-news-15/listening.htm.

Re:If it's anything like fusion...

[Anonymous Coward]

Quantum computing (general purpose computing) is at least 50 years away by most estimations.
Quantum special purpose circuits will be a bit closer. Maybe 20 years as you say.
You'd need millions of qubits to do useful computation (faster than silicon). Right now we are more or less at 1 logical qubit.
Some people have on the order of 100 physical qubits, but that doesn't really help for logical qubits.

Re:If it's anything like fusion...

[MouseR]

Quantum computing will never be observed. Every time we look at it, the expectation changes.

Re:If it's anything like fusion...

[angel'o'sphere]

The primary reason that fusion has stayed far away has been a demonstrated lack of funding.
I don't think so.

On a single reactor you can not do more experiments than X, regardless of funding.

And I'm not convinced it makes sense to have multiple reactors of the same kind.

Bottom line a reactor takes decades to build. That can not really be improved by "funding".

Ofc a bit more money, even double of it, might have helped, but thats it.

Re:If it's anything like fusion...

[Sax Russell 5449D29A]

For a pun like that you deserve a promotion at work. :-)

Re:If it's anything like fusion...

[RespekMyAthorati]

I will definitely make a poster of that.
And credit it to Einstein, of course.

Re:Quantum computing in layman's terms

[JoshuaZ]

Quantum computing can be described as a method, a technique, which allows for the computer for a given task to take a peak into the future and to read the answer from the future back to the present.

This is completely wrong. There are in fact computational models that have been worked out about what a computer that could peak into the future would be like and they are insanely more powerful than quantum computers. See http://www.scottaaronson.com/papers/ctc.pdf. Quantum computing has nothing remotely like what you've said. I suggest for an actual primer on the topic reading Scott Aaronson's excellent book "Quantum Computing Since Democritus" which doesn't require anything beyond a little basic linear algebra. And in the meantime, if you don't know much about a topic, maybe don't make extreme policy suggestions?

Re:Quantum computing in layman's terms

[alvinrod]

Alternatively, this video does a reasonable job at outlining how a quantum computer works. It doesn't go into too much detail, but it's probably enough to give the average person an idea of the differences between quantum and classical computers.

Re:Quantum computing in layman's terms

[110010001000]

If you can't use the word "peek" properly you shouldn't be commenting on computer related issues at all.

Is quantum computing within reach?

[PopeRatzo]

Well, it is and it's not.

Real Quantum computing in layman's terms

[Anonymous Coward]

Sadly no.

Quantum Physics is not science, more religion. Experiments to prove quantum entanglement prove it does not happen (e.g. the latest Delft experiment), and so Delft filtered the experiments for times of 'successful entanglement'. In other words filtering for the effect you're trying to prove then using those experiments as proof of the effect.

A photon of light never did change it's nature depending on the detector it hit. That change of nature never did propagate backwards in time and then forwards again to everything it interacted with. That was only ever the limits of the detector mapped onto the measurement.

An electron is never is all places simultaneously until detected. Where you detect it is just the limits of the detector mapped onto the thing being detected.

From discussions here, It's clear that many physicists don't even understand how a photo-multiplier works. Or understand that you could never have a zero energy gap detector because it would firing continuously. Hence you'll always fail to detect events below that energy gap in the detector.

Quantum computers (e.g. DWave) are analogue computers running annealing algo in hardware. They don't work instantaneously (no entanglement), they don't always get the correct result, (i.e. not in all states simultaneously, no quantum effect). Yet that is the properties you would expect.

"Yes, quantum entanglement exists, nobody can explain why/how."

Are you shitting me? They even put a filter in the circuit to select only the subset of experiments that will give them the result they seek! When you read the Delft paper they try to justify at length filtering the results. Which suggests they know its broken. The only entanglement between the two photons is the experimenters filtering!

It's the classic mistake, you have a flock of starlings, your detector can only see flocks and not individual birds. It sees the flock darting around, travelling faster than light, sometimes in two places, sometimes none. IT'S JUST THE ENERGY GAP IN THE DETECTOR MAPPED ONTO THE MEASUREMENT. If you could see the individual birds you'd understand.

Re:Real Quantum computing in layman's terms

[Anonymous Coward]

I'll admit I don't know anything about this Delft experiment, other than confirming that's a real thing that says the exact opposite of what you're saying. Your criticism sounds like something that could be true, but I'm doubtful on the basis that everything else you said is a non-sequitur. I particularly like this one:

they don't always get the correct result, (i.e. not in all states simultaneously, no quantum effect).

What?

Re:Real Quantum computing in layman's terms

[Anonymous Coward]

DWave is an optimizer. It runs an annealing algorithm. An optimizer tries to solve a user function to find the best solution. e.g. what value of (x1,x2,x3,x4,x5...) would return the minimum of my function F(x1,x2,x3,x4,x5...).

In DWave the function is a magnetic circuit, defined by connections. You define the connections, the magnetic field collapses, and settles on a minimum result for F. You then measure x1,x2,x3.... to see what inputs gave that result.

A classic Feyman theoretical quantum computer has photons, or electrons in all states simultaneously until detected. So x1,x2,x3 are in all states until the collapse, including the state that would give the optimal minimum. So such a computer would always find the optimal result and always collapse to that optimal result. i.e. it's not a quantum computer, its an analogue magnetic computer. The undetected electrons are in ONE state, not ALL states, i.e. no superimposition.

DWaves vague claims of entanglement between QBits, I've never seen fleshed out into a paper. Entanglement has been theorized at least 1000x faster than the speed of light and thus would be instantaneous to us (we can only measure at the speed of light). Yet it doesn't work instantaneously.

Delft experiment sadly is now behind a paywall, but it emitted a photon X1 from an electron e1, 1.3km apart it emitted a second photon X2 from an electron e2.
Those photons were brought together and 'entangled'. Now e1 was checked and had state S1 and e2 was checked and had state S2 and by 'entanglement' S1 and S2 were complementary. i.e. the act of detected e1's state had rippled backwards through space time to make e2's state complementary to e1. Since this happened above a certain probability threshold (aka Bells Threshold), then entanglement was real.

Except it didn't. Delft took the results and it was below the Bells threshold, so they filtered for only the experiments where the photons X1 and X2 could be detected as the same in all possible ways (.e.g phase etc).

So if X1 and X2 are the same, then e1 and e2 are the same, and the entanglement is the filtering.

This is religion no science.

Re:Real Quantum computing in layman's terms

[Anonymous Coward]

The AC you replied to is a re-occurring Slashdot crackpot or troll(s). They copy-paste the same thing over and over again, sometimes changing a lot or a little, while completely disregarding posts that point how how fundamentally wrong their armchair theories are. It is great that someone wants to think about things and ask questions, but when they show zero interest in answers, or experiments that directly contradict their theories (including basic ones that conflict with his starlings idea of photons, something an undergrad physics student would get hands on experience with in a standard lab course)... then they are venturing into crackpot territory. Searching Slashdot stories for some of the wording, like "starlings" and "quantum" together, and you can find many ignored, detailed, referenced posts pointing out why they are wrong, which get ignored. He often somehow gets modded up, seemingly through spamming the same posts faster than people with the time and knowledge to carefully rebut them (and only to be ignored, so not much motivation to waste as much time posting).

Re:Real Quantum computing in layman's terms

[JoshuaZ]

Pretty much everything you've said is wrong. Yes, the Delft experiment used filtering. No, the filtering doesn't do what you think it does. But more to the point, there have been many experiments prior to the Delft experiment that didn't use that sort of filtering and still got results consistent with entanglement. See e.g. http://www.nature.com/nature/journal/v409/n6822/abs/409791a0.html for an example.

Re:Quantum computing in layman's terms

[angel'o'sphere]

I think there is a reason why I gave you a red dot.

I did not even notice that he mistyped peek with peak.

But thank you that your intellect is so smart that you see typing errors but so dim that you don't grasp the meaning of what he said.

I for my part usually don't see typing errors ... and I'm happy that my browser underlines wrong spelled words red or redly or read ... hm, seems the underlining failed ... what did I want to say?

Re:Quantum computing in layman's terms

[JaredOfEuropa]

At the same time there is a consensus that Superluminal communication (faster-than-light) is considered impossible.

It has been proven (within our understanding of physics) that being able to send messages faster than light allows you, between certain weird reference frames, to send a message back in time, breaking causality. But I'm not sure how fundamental causality is to our physics models, or if our models actually allow for exceptions.

Sort of similar to the crap about time paradoxes and killing your own father. There is no paradox, and killing your father won't make you slowly fade out like in the movies. Cause precedes effect; you kill your dad but there is nothing in the past to cause that instance of "you" to disappear; the cause of you appearing in the past lies in the future and removing it doesn't affect that event. Unless time has a garbage collector to sweep up any dangling pointers like yourself. Anyway, I better go and have another cup of coffee.

Re:Quantum computing in layman's terms

[ReallyNiceGuy]

My take on time travel is that it is impossible. Here is my reasoning: the universe is constantly evolving, be it's wave function or thermodynamically. To move backwards in time, you have to reverse the state of the universe to that of your choosing. To do that, you have to do work. Think about the amount of energy necessary to move all particles of the universe 1 second to the past. Besides, you don't know the state of the universe, not because you don't have enough information, but on principle it is impossible to know (quantum mechanics).
IANAP

Re:Quantum computing in layman's terms

[Guignol]

I know what you mean, but
This wasn't just any "your everyday typo"
I mean, peek and poke... you know ?
I would also have a hard time being convinced by anyone unfamiliar with how to write peek to have much of a deep insight about computers... and quantum computing at that
I think you were replying to a sort of joking/not so joking reply
But I could be wrong and this could just be our regular grammar nazi :) you probably red-doted him for some reason before after all...

Re:Quantum computing in layman's terms

[110010001000]

It isn't a typing error. The words "peek" and "poke" are fundamental to computing. If you repeatedly use "peak" instead of "peek" then you don't have any sort of basic knowledge of computing. In addition, his description is nonsensical.

I know what to name it

[Jahat]

Schrödinger's Quark

Re:Entangle enough at once and how does it feel?

[shaitand]

"Since a single electron isn't sentient, it likely feels nothing, and cannot report on how it felt."

That's a bold assumption. Human beings used to think birds had no notable intelligence and birds can actually create words/sounds and use them in fairly obvious forms of meaningful communication. Who could say what complexity lives beyond the event horizon of the noble electron. That is like making the assumption that a massive bolder isn't sentient. The complex processes undergone by a bolder and the changes over time are certainly as complex as those undergone by a person or animal but the timescale is such that it is likely a bolder couldn't even perceive you if you were sentient. You would seem no more likely to be sentient to the bolders and mountains of the world than the electron is to you. How could anything that flits in and out of existence so rapidly and has no notable lasting impact be complex let alone sentient?

Is it really so difficult for people to grasp the concept of relative perspectives and timescales?

Re:Quantum computing in layman's terms

[amRadioHed]

The words "peek" and "poke" are fundamental to basic programming from three decades ago. What modern languages use those terms?

Re:Quantum computing in layman's terms

[angel'o'sphere]

ofc it is an typing error, how dumb are you?
Even native english speakers make typing errors of that kind.
I make hundreds of them every day in my own native language, because my fingers seem just to hear what my brain is thinking loud.
No idea what the psychological reason behind errors like that is.

I'm hundred percent sure if you ask the author of the post that makes you so upset:
a) define the meaning of peak
b) define the meaning of peek
He perfectly defines it.

Bottom line you are one of the idiots if he would have been my teacher in school, who was always very close that I lost temper and killed him.

And as the other people pointed out: peek has absolutely no meaning in languages besides (some dialects of) BASIC, hence your complete threat^Hd of moronic posts is nonsense.

Re:Quantum computing in layman's terms

[angel'o'sphere]

Well, my personal typing error I was working on the last 2 years is 'where' and 'were'.
And yes, my brain knows the difference since I started to learn english which was 40 years ago.
My fingers don't, my eyes don't. So now some fucking thing, no idea where it actually came from and how to apply it to other typing errors always makes me stop typing after a 'were' or 'where'.
Usually I type 'where', where a 'were' is appropriated. And remove the 'h'.

That is why it makes me upset if people try to proclaim other people to be dumb and not grasp the difference between it, is, its and it's.

Yes, in my eyes he is an idiotic grammar/spelling Nazi.

I believe I red dotted him because of idiotic claims regarding computing/software development/software processes. Especially as his name tries to indicate he is an expert on those topics.

Language is a very complex issue. And unfortunately americans are particular dumb in accepting or realizing that.

E.g. what is worn (oh, just found this type, obviously that was meant to mean wrong, but worn is a legal word so it is not red underlined, was just about to press submit) with this two sentences: I do not like she! She do not like I!
In english everything, In Thai, Chinese, Japanese, they are perfectly correct, besides word ordering and a marker syllable here and there.
That you have to replace he for him, she for her, I for me, is a concept that does not exist in those languages.
I'm german, so it is no problem for me, as my language is similar to english. (Or other way around, english is 25% german anyway).