Breakthrough Toward Quantum Computing
Soulskill posted more than 2 years ago  from the advancinginfundamentalincrements dept.
61redwolfe7707 writes "Qubit registers have been a hard thing to construct; this looks to be a substantial advance in the multiple entanglements required for their use. Quoting: 'Olivier Pfister, a professor of physics in the University of Virginia's College of Arts & Sciences, has just published findings in the journal Physical Review Letters demonstrating a breakthrough in the creation of massive numbers of entangled qubits, more precisely a multilevel variant thereof called Qmodes. ... Pfister and researchers in his lab used sophisticated lasers to engineer 15 groups of four entangled Qmodes each, for a total of 60 measurable Qmodes, the most ever created. They believe they may have created as many as 150 groups, or 600 Qmodes, but could measure only 60 with the techniques they used.'" In related news, research published in the New Journal of Physics (abstract) shows "how quantum and classical data can be interlaced in a realworld fiber optics network, taking a step toward distributing quantum information to the home, and with it a quantum internet."
First Quantum Post (0)
GameboyRMH (1153867)  more than 2 years ago  (#36803138)
Users on quantum PCs will see a dirty joke in place of this text.
Re:First Quantum Post (1)
blair1q (305137)  more than 2 years ago  (#36803274)
But not if they actually try to read it.
Re:First Quantum Post (1)
Schmorgluck (1293264)  more than 2 years ago  (#36803638)
Actually, since you couldn't know for certain that your post would be first before you had posted it, it was in a quantum state of being first and notfirst until you collapsed its wave function by posting it.
Or something like that...
Re:First Quantum Post (0)
Anonymous Coward  more than 2 years ago  (#36806048)
car
clown
elephant
bar
frown
excrement
thank you
Quantum Internet? (0)
Synn (6288)  more than 2 years ago  (#36803164)
Quantum internet, really? Will I be eating Quantum pop tarts while I surf Quantum porn?
Re:Quantum Internet? (1, Funny)
clyde_cadiddlehopper (1052112)  more than 2 years ago  (#36803210)
Re:Quantum Internet? (0)
tom17 (659054)  more than 2 years ago  (#36803238)
Are you saying you like *dead* stretched anuses?
Maybe?
Re:Quantum Internet? (1)
Alsee (515537)  more than 2 years ago  (#36805568)
Quantum link to goatse... you don't know if you saw it or not, but you're absolutely certain that you don't want to know.

Re:Quantum Internet? (1)
Greyfox (87712)  more than 2 years ago  (#36805692)
Re:Quantum Internet? (1)
Thing 1 (178996)  more than 2 years ago  (#36807250)
Hmm. Looks like a wormhole...
What, Morgan Freeman's?
Re:Quantum Internet? (1)
Lanteran (1883836)  more than 2 years ago  (#36806052)
Re:Quantum Internet? (2, Funny)
Anonymous Coward  more than 2 years ago  (#36803230)
Quantum porn?
He or She does all possible things with another He or She all at once. If you really like what you see, don't blink because it will be something different by the time your eyelids open back up.
Re:Quantum Internet? (0)
Anonymous Coward  more than 2 years ago  (#36803842)
Re:Quantum Internet? (0)
Anonymous Coward  more than 2 years ago  (#36803906)
And what's more, they're always in a super position...
Re:Quantum Internet? (1)
Dogtanian (588974)  more than 2 years ago  (#36804952)
Quantum porn?
He or She does all possible things with another He or She all at once. If you really like what you see, don't blink because it will be something different by the time your eyelids open back up.
You mean like a pornographic version of that Doctor Who episode with the scary statues?
Re:Quantum Internet? (1)
vlm (69642)  more than 2 years ago  (#36803240)
Quantum internet, really? Will I be eating Quantum pop tarts while I surf Quantum porn?
It will almost certainly be the marketing term of the decade.
Much as I had "turbo sunglasses" in the 80s, because nothing says glare reduction than an turbocharger, and I bought a nano "ipod" some years ago, i as in internet when ironically its probably the only piece of consumer enduser electronics apple sold that decade without a web browser.
I'm sure I'll see stickers to put on my quantum computer that somehow make it faster, and quantum tennis shoes, RSN.
Re:Quantum Internet? (1)
Dogtanian (588974)  more than 2 years ago  (#36805288)
I bought a nano "ipod" some years ago, i as in internet when ironically its probably the only piece of consumer enduser electronics apple sold that decade without a web browser.
Sure, but remember the "i" prefix originated (as far as Apple were concerned) with the original iMac, not the iPad. The former was Apple's "comeback" product and culturally prominent at the time (remember the late90s translucent coloured plastic fad it sparked). In that case it *did* supposedly stand for "Internet".
I'm assuming that the name "iPod" was then chosen to piggyback on the success and name recognition of the iMac, regardless of whether the "i" was relevant. The fact that the iPod was even more successful than the iMac makes it easy to forget that it didn't originate Apple's iNaming scheme(!)
Re:Quantum Internet? (1)
narcc (412956)  more than 2 years ago  (#36808620)
In the before time, in the long long ago, we had tons of stuff prefixed with "e" or "i"  how Apple managed its now near monopoly on that particular lowercase vowel prefix is anyone's guess.
Re:Quantum Internet? (1)
Sulphur (1548251)  more than 2 years ago  (#36808846)
In the before time, in the long long ago, we had tons of stuff prefixed with "e" or "i"  how Apple managed its now near monopoly on that particular lowercase vowel prefix is anyone's guess.
Favorite letter?
Re:Quantum Internet? (0)
Anonymous Coward  more than 2 years ago  (#36803396)
Quantum porn: 50% chance of being straight porn, 50% chance of being gay porn, and you don't know which it turns out to be until you are "done".
Re:Quantum Internet? (1)
equex (747231)  more than 2 years ago  (#36803768)
Re:Quantum Internet? (0)
Anonymous Coward  more than 2 years ago  (#36804324)
Because you can't know if a quantum joke is good or bad until you posted it.
Re:Quantum Internet? (1)
ThePeices (635180)  more than 2 years ago  (#36803424)
"Quantum internet, really? Will I be eating Quantum pop tarts while I surf Quantum porn?"
No, you will not be going down on slutty pop music singers while looking at porn on a quantum computer.
You are just not an Alist celebrity.
Re:Quantum Internet? (1)
mrops (927562)  more than 2 years ago  (#36804274)
You wouldn't know if its a porn or a preacher giving a sermon until you hit play, and then as soon as you observe it, it won't be either.
Re:Quantum Internet? (1)
tsotha (720379)  more than 2 years ago  (#36806488)
*stare* (2)
Spigot the Bear (2318678)  more than 2 years ago  (#36803166)
Obligatory: But Will It Ecrypt My Google Mail (0)
Anonymous Coward  more than 2 years ago  (#36803176)
so the N.S.A [youtube.com] can't eavesdrop?
Yours In D.C.,
K. Trout
Re:Obligatory: But Will It Ecrypt My Google Mail (1)
peragrin (659227)  more than 2 years ago  (#36804976)
Sure but china has already hacked your password anyway so there isn't much point.
How do they work? (2)
Normal Dan (1053064)  more than 2 years ago  (#36803196)
Re:How do they work? (1)
Anonymous Coward  more than 2 years ago  (#36803284)
Typically, yes, but this can be more useful than it sounds! What you want to do is perform a number of quantum operations [wikipedia.org] such that, when you do measure your qubit, you will get the answer you want with probability >0.5. The operations you can perform on a qubit are very limited (you'll notice there are no AND operations, OR operations or anything that would allow you an IF statement) and you almost never get answer that's correct with absolute certainty, but they could still be fantastically useful. With just a few operations you can sometimes coerce a qubit into a state such that it will give you correct answer with probability between 0.5 and 1.0. Once you have that, it's just a matter of repeating the computation enough times to be confident.
Re:How do they work? (2)
vlm (69642)  more than 2 years ago  (#36803476)
How would one read the output of a quantum computer if they quantum state changes upon observation? Wouldn't it just spit out random numbers?
One term to google for is decoherence.
The two paragraph wikipedia answer is at:
http://en.wikipedia.org/wiki/Quantum_computer#Operation [wikipedia.org]
The multipage answer at quantiki is at:
http://www.quantiki.org/wiki/Basic_concepts_in_quantum_computation#Decoherence_and_recoherence [quantiki.org]
My crappy slashdot car analogy is the internal state of my car is almost infinitely complicated, O2 sensor levels and thermostat bypass fractions. But you could theoretically compute an algebraic equation that boils down to can I drive 400 miles on a tank of gas? The answer at the end is, is the engine running or not, just one binary bit. All the hidden internal variables and states, zillions of them, like coolant temp, O2 loop state, etc, all collapse down to one bit. Its not really important what the internal state is when the engine shuts off, or if it shut off because the O2 loop leaned out of spec, or the fuel pump control loop when haywire when it sucked air, or...
So, a 1024 qubit computer has 2^1024 internal variables all of a vaguely analog complex number value, and those 2^1024 values collapse down to a mere 1024 bits when you factor my RSA key... There's a darn near infinite number of possible values that collapse down to 1024 bits and you randomly get one of them.
Re:How do they work? (0)
Anonymous Coward  more than 2 years ago  (#36803534)
quantum computers are probabalistic rather than deterministic... take a single qubit for example, it can be a zero, a one ir a linear superposition of the both... when we measure a quantum system, its wavefunction collapses into one of the 2 states: a 1 or a zero. You then average across multiple readings to get the actual value... For example, say the qubit was in an equal superposition of 1 and 0.. that means when we measure, the probability of getting a 1 is 0.5 and tge probability of getting a zero is 0.5 . If we average across a large enough ensemble we recover the state of being in an equal superposition.
Re:How do they work? (0)
Anonymous Coward  more than 2 years ago  (#36805676)
A qubit in an eigenstate (1 or 0) will remain in that state until the state is destroyed (by measuring a complimentary variable).
Re:How do they work? (3, Informative)
Alsee (515537)  more than 2 years ago  (#36805460)
We can compare it to rolling dice, where the dice can be loaded to shift the percentages. If we put a weight on the 1, we might roll a 1 half the time and randomly get 2 through 6 the rest of the time. In quantum mechanics we can preform calculations that change how the dice are loaded. Ideally, we can load the die so strongly that 2 through 6 are driven down to zero percent, and 100% of the time we "randomly" roll a 1.
Depending on the particular problem and the particular technology used, certain parts of the computer might not be working with a perfectclean 100%. Particular parts of the computer might have the dice loaded to 99.9% randomly roll a particular result. Obviously we don't want a computer that's oly 99.9% right :D
Different kinds of quantum computers deal with that in different ways. The simplest example is a quantum computer that works on a beam of photons or something. A beam of light might contain a trillion photons per nanosecond. If 99.9% of those photons randomly come out on the right answer, the right answer obviously lights up brightly. The 0.1% of photons lighting up the various wrong answers will be too dim to notice.
For some quantum calculations they use the very simple technique of just running it a dozen times or something. There's basically a 99% chance you'll get a dozen matching correct answers, and a 1% chance you'll get eleven matching correct answers and one random error that you throw away. There is a minuscule chance you'll get (and throw away) two or possibly three garbage results out of the dozen, but the only way you would ever get a wrong answer from that is if the same wrong answer came up seven or more times at once, and mathematically that won't happen a million or billion years.
However for a "real" desktoptype quantum computer, there's a much more complicated and powerful technique they would build in.... error correcting bits and error correcting codes. By adding in a few extra bits, the computer can automatically spot and correct any random wrong values as soon as the appear. All of the automatic error correction stuff might make the computer something like 50% bigger or maybe twice the size, but it can easily match the (effectively zero) error rate of standard computers.

Re:How do they work? (0)
Anonymous Coward  more than 2 years ago  (#36808502)
For some quantum calculations they use the very simple technique of just running it a dozen times or something. There's basically a 99% chance you'll get a dozen matching correct answers, and a 1% chance you'll get eleven matching correct answers and one random error that you throw away. There is a minuscule chance you'll get (and throw away) two or possibly three garbage results out of the dozen, but the only way you would ever get a wrong answer from that is if the same wrong answer came up seven or more times at once, and mathematically that won't happen a million or billion years.
Mostly correct, but one minor point: Most of the calculations we want to use quantum computers for give answers that are easy to verify and so you usual only need to run the program once. Factorization, for example, (although Shor's algorithm is actually more complicated than this) the quantum algorithm gives you the factors and then a classical computer can be used to check the result. If the result is wrong, you just rerun the program, but unless it is, you don't need to.
Re:How do they work? (1)
mgiuca (1040724)  more than 2 years ago  (#36867902)
Couldn't you also use a regular computer to verify it with 100% accuracy (for some classes of problems)?
For example, I can (as I understand it) use a quantum computer to find the two prime factors of a semiprime number. Say that the QC can give me the correct answer with, say, 60% accuracy. Now I just need to take the answer and use a regular computer to multiply the two numbers and see if they give me the original number. If they don't, I ask the QC again until it gets it right. No need to continuously run the computation to reduce the probability of error. Is there some reason this might not work?
Re:How do they work? (1)
Alsee (515537)  more than 2 years ago  (#36881128)
Yes, for most kinds of problems a normal computer can quickly verify whether a quantum result is correct. However I don't think a normal computer can verify certain kinds of "nonexistence" or "optimum" results. For example if you plug in a problem and the quantum computer says no solution exists, a normal computer can't confirm that. Or if you plug in a traveling salesman problem asking for the shortest route and it gives you a shortroute answer, a normal computer can obviously calculate the length of that route, but the normal computer generally can't verify that no shorter route exists.

Re:How do they work? (1)
mgiuca (1040724)  more than 2 years ago  (#36882308)
Thanks! Very informative. And ... Slashdot requires that I say more than just this. Hmm. Extremely informative?
Re:How do they work? (0)
Anonymous Coward  more than 2 years ago  (#36811396)
The quantum state doesn't always change upon observation. It depends on what physical property you measure and what physical property the state characterizes (in technical terms "of which it is an eigenstate"). So it is really connected to the Heisenberg "uncertainty" principle: for example, if you know the position of a quantum system (ie its quantum state is a position eigenstate), then measurement of its momentum (mass times velocity in classical physics) become random. However, measurements of its position will give nonrandom, ultraprecise results in the absence of backaction (another story).
Note that quantum physics can be used to perform measurements that are much more sensitive and precise than classical measurements, so the inherent randomness of quantum mechanics (The Old One playing at dice as Einstein put it) do not preclude extremely precise observations... and computations!
um... (1)
Charliemopps (1157495)  more than 2 years ago  (#36803248)
Re:um... (5, Informative)
jmizrahi (1409493)  more than 2 years ago  (#36804754)
imagine a beowulf makerbot.. (1)
decora (1710862)  more than 2 years ago  (#36803322)
of these things...
Price Pfister? (1)
nog_lorp (896553)  more than 2 years ago  (#36803350)
am I the only one ? (1)
Chuby007 (1961870)  more than 2 years ago  (#36803444)
Re:am I the only one ? (0)
Anonymous Coward  more than 2 years ago  (#36803496)
Yeah. No clue here.
Re:am I the only one ? (0)
Anonymous Coward  more than 2 years ago  (#36804062)
Beats the hell outa me what it means or how it would apply to me! Maybe it's like Google's
"Feeling Lucky" search, you take whatever comes along!
Fucking Qubits... (0)
Anonymous Coward  more than 2 years ago  (#36803766)
Fucking Qubits, how do they work?
Re:Fucking Qubits... (1)
maxwell demon (590494)  more than 2 years ago  (#36804150)
You don't want your qubits to fuck. When they fuck, they don't work.
But maybe that's why we have so much trouble with getting more qubits. If we let them fuck, maybe they'll multiply by themselves!
Level 60!?! (1)
Kamiza Ikioi (893310)  more than 2 years ago  (#36803948)
I never got past level 3 in Qbert! First Pacman, then Donkey Kong, now Qbert. This is getting serious.
I'll believe it when I see it. (0)
Anonymous Coward  more than 2 years ago  (#36805064)
Right now, quantum computers are much further from reality than human level AI. The problem is decoherence, something that cannot be overcome unless we essentially either A) find an existing physical system in biology that overcomes it or B) rewrite the laws of physics to gain a better understanding of QM. Physicists are headed in exactly the wrong direction with their current superstring theories and Mtheory. If they would just let the math guide them, the solution would be obvious. Instead, their mathematics just gets increasingly complicated. I'm not holding my breath for quantum computers.
Re:I'll believe it when I see it. (1)
Wandering Idiot (563842)  more than 2 years ago  (#36807926)
Re:I'll believe it when I see it. (1)
Maritz (1829006)  more than 2 years ago  (#36813600)
Physicists are headed in exactly the wrong direction with their current superstring theories and Mtheory. If they would just let the math guide them, the solution would be obvious.
Please, elaborate. In detail. I wouldn't understand but it would be fun to try and ask someone who would understand to put it into thick bastard terms for me. You ought to drop a quick email to the likes of Brian Greene, Ed Witten etc if you get a minute.
this is not a breakthrough... (1)
Gravis Zero (934156)  more than 2 years ago  (#36806136)
it's a quantum leap. :)
Hey... (1)
tsotha (720379)  more than 2 years ago  (#36806492)
Got $10 million? Was: Re:Hey... (0)
Anonymous Coward  more than 2 years ago  (#36807018)
http://www.engadget.com/2011/05/18/dwaveoneclaimsmantleoffirstcommercialquantumcomputer/
Re:Hey... (1)
Sulphur (1548251)  more than 2 years ago  (#36808886)
How many of these "breakthroughs" are going to have to happen before I can actually buy something. It's like a breakthrough and not a breakthrough at the same time.
As soon as they get 640k qbits. No one will ever need more than that.
Quantum mechanics is... (1)
jamiesan (715069)  more than 2 years ago  (#36807094)
Que the Sam Beckett jokes (1)
PDX (412820)  more than 2 years ago  (#36808074)
If the wmap cold spot is an alternate universe then a tachyon beam might be able to break past dimensional barriers that exist between universes. If the other universe has two cold spots then a hub of data could be formed. Imagine the total output of every universes' data collections piped across dimensional barriers. The rate of data is limited by the phase data and the rotation of the beam. Multiverse theory has proved correct. The downside is not knowing if anyone can survive in the other universe. The challenge is to detect FTL signals.
LOL cats (1)
jjbarrows (958997)  more than 2 years ago  (#36809604)
Will I get a quantum camera... (1)
gestalt_n_pepper (991155)  more than 2 years ago  (#36809948)
to see what might have been?
Bad description of entanglement (1)
harryjohnston (1118069)  more than 2 years ago  (#36820094)
From TFA: "imagine that two people, each tossing a coin on their own and keeping a record of the results, compared this data after a few coin tosses and found that they always had identical outcomes, even though each result, heads or tails, would still occur randomly from one toss to the next". That's badly wrong. (Although I'm sure the researcher understands quantum mechanics, it was probably the PR guy who got it wrong!)
Entanglement really isn't all that mysterious; it just seems strange if you haven't gotten your head around noncommuting observables. Entangled particles are the quantum analogue of classical correlations  so it isn't as if two people are tossing separate coins, which of course aren't correlated.
Instead, imagine choosing a playing card at random from a shuffled deck and (without looking) cutting it in half and putting the two halves in separate envelopes. Keep one envelope and send the other to a friend living near Alpha Centauri. Open the envelopes at the same (prearranged) time. Gee whiz, you both simultaneously see two halves of the same card. Magic! (Well, maybe not.)
That's the classical playing card. A quantum playing card is weird: you can't see whether the card is black or red and whether it is odd or even at the same time. If you find out whether the card is black or red the number on the card changes at random; if you find out whether it is odd or even the suit of the card changes at random. Just to really make things awkward, you can choose to make a measurement that one third looks at the card's colour and two thirds looks at whether the card is odd or even (yes, I know that doesn't even make sense but that's the way it works). Then ... if you cut a whole bunch of cards in half, do different measurements each time, and take care of a few loopholes, you find that the statistics you get prove that until you looked at each card (or half of it) it didn't actually have a specific colour or a specific number, just a wavefunction describing the probabilities. This is called Bell's Inequality.
My advice: if you don't need to understand it, don't bother trying. The important point is that it's the quantum cards (noncommuting observables) that are weird, not the fact that you can cut them in half (entanglement).
(Incidentally, if the card has been cut into two, and you look at the colour of each half, the numbers on the two halves change independently of one another. The entangled cards aren't mystically bound together forever. Only the initial measurement is the same.)