Qbits 30 Meters Apart Maintain Entanglement Across Refrigeration Systems (arstechnica.com) 40
"A new experiment uses superconducting qubits to demonstrate that quantum mechanics violates what's called local realism," reports Ars Technica, "by allowing two objects to behave as a single quantum system no matter how large the separation between them."
The experiment wasn't the first to show that local realism isn't how the Universe works — it's not even the first to do so with qubits. But it's the first to separate the qubits by enough distance to ensure that light isn't fast enough to travel between them while measurements are made. And it did so by cooling a 30-meter-long aluminum wire to just a few milliKelvin. Because the qubits are so easy to control, the experiment provides a new precision to these sorts of measurements.
And the hardware setup may be essential for future quantum computing efforts... Everyone working with superconducting qubits says that we will ultimately need to integrate thousands of them into a single quantum computer. Unfortunately, each of these qubits requires a considerable amount of space on a chip, meaning it gets difficult to make chips with more than a few hundred of them. So major players like Google and IBM ultimately plan to link multiple chips into a single computer (something the startup Rigetti is already doing).
For tens of thousands of qubits, however, we're almost certainly going to need so many chips that it gets difficult to keep them all in a single bit of cooling hardware. This means we're going to eventually want to link chips in different refrigeration systems — exactly what was demonstrated here. So this is an important demonstration that we can, in fact, link qubits across these sorts of systems.
Or, as long-time slashdot reader nounderscores puts it, "Imagine a beowulf cluster of these.
"The Qbits that Simon Storz et al at ETH Zurich entangled at the ends of 30m of cryogenically chilled wire not only put the last nail into the coffin of hidden variable theory by being so far apart, they also allow quantum computing to scale to multiple refrigeration systems."
And the hardware setup may be essential for future quantum computing efforts... Everyone working with superconducting qubits says that we will ultimately need to integrate thousands of them into a single quantum computer. Unfortunately, each of these qubits requires a considerable amount of space on a chip, meaning it gets difficult to make chips with more than a few hundred of them. So major players like Google and IBM ultimately plan to link multiple chips into a single computer (something the startup Rigetti is already doing).
For tens of thousands of qubits, however, we're almost certainly going to need so many chips that it gets difficult to keep them all in a single bit of cooling hardware. This means we're going to eventually want to link chips in different refrigeration systems — exactly what was demonstrated here. So this is an important demonstration that we can, in fact, link qubits across these sorts of systems.
Or, as long-time slashdot reader nounderscores puts it, "Imagine a beowulf cluster of these.
"The Qbits that Simon Storz et al at ETH Zurich entangled at the ends of 30m of cryogenically chilled wire not only put the last nail into the coffin of hidden variable theory by being so far apart, they also allow quantum computing to scale to multiple refrigeration systems."
What does that mean? (Score:2)
Re:What does that mean? (Score:5, Informative)
Not exactly. These are quantum "gyroscopes" so they're spinning both ways at once until you measure them. And they're entangled, so when you check them they're always spinning opposite ways. This is a test of Bell's inequality - the maths is a bit above my head, but it proves that they were really spinning both ways at once until you checked rather than always spinning in only one way and you didn't know which one. The extra part in this experiment is that the two qubits were 30m apart, 100ns at light speed, and they made the measurements in under 100ns so there is no way that one qubit was telling the other one that you'd measured it.
This proves that qubits can be in multiple states at once, go to only one state when you measure it, and the other qubit goes to the opposite state faster than a light-speed signal could reach it. Thus qubits don't obey classical causality.
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The only reason to claim that before you measured it that they were spinning both ways at once is because you simply did not know which way they were spinning. I can claim the same results by taking a black and white marble and putting them randomly into two boxes. Until you open one you don't know the color of the other one.
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The only reason to claim that before you measured it that they were spinning both ways at once is because you simply did not know which way they were spinning. I can claim the same results by taking a black and white marble and putting them randomly into two boxes. Until you open one you don't know the color of the other one.
Yep. This is the bit I've never understood about entanglement.
How do you know the states changed at the instant you looked at one of them instead of a nanosecond after they were "entangled"? There's no way to know that.
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The only reason to claim that before you measured it that they were spinning both ways at once is because you simply did not know which way they were spinning. I can claim the same results by taking a black and white marble and putting them randomly into two boxes. Until you open one you don't know the color of the other one.
Yep. This is the bit I've never understood about entanglement.
How do you know the states changed at the instant you looked at one of them instead of a nanosecond after they were "entangled"? There's no way to know that.
This is the very heart of bells inequality. The short of it is that if the particles were handed a secret “spin up” and “spin down” cards at the instant of entanglement, that the choice of orientation of the measurement wouldn’t matter, but it does. One could also argue that the universe just conspires to correlate the probability because the operators don’t have free will as they are bound by physics, so the orientation of the measurement is chosen randomly for Alice a
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What's "the choice of orientation of the measurement"?
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The best way to understand what is strange about QM is to look at GHZ states, which involve three particles. If you can do measurements along different axes and get 1 or -1 as result. If you do measurements along X axis for all particles you get results which appear to be randomly 1 or -1, but if you multiply the results you always get -1. Now so far, this could be explained by just a random starting configuration which is consistent with having the product -1. But if you change the measurements and do meas
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but it proves that they were really spinning both ways at once until you checked
More specifically it means they only exist as correlated probability amplitudes until a measurement resolves the certainty to 100%. The correlation is *instant at the time of certainty and exceeds the speed of light which is how it can be shown the classical view of local realism can’t be the sole explanation. We don’t know that they exist in both classical states simultaneously.
*Instant gets very complicated when you add time dilation and we don’t have a good idea of what happens if
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The extra part in this experiment is that the two qubits were 30m apart, 100ns at light speed, and they made the measurements in under 100ns so there is no way that one qubit was telling the other one that you'd measured it.
This experiment reminds me of the equally pointless "cosmic bell test" experiment. Some seem to be interested in conducting experiments in which everyone knows full well in advance what the answers will be. Almost as if people are looking for an excuse to write easy papers with assured outcomes so as not to strain themselves.
This proves that qubits can be in multiple states at once, go to only one state when you measure it, and the other qubit goes to the opposite state faster than a light-speed signal could reach it. Thus qubits don't obey classical causality.
Not quite. Light speed only applies to things propagating through space. In this case nothing is traveling.
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This experiment reminds me of the equally pointless "cosmic bell test" experiment. Some seem to be interested in conducting experiments in which everyone knows full well in advance what the answers will be. Almost as if people are looking for an excuse to write easy papers with assured outcomes so as not to strain themselves.
Oh please. This is how science is always done. If the test has never been performed in this way we cannot "knows full well in advance what the answers will be" just what we expect. Also, it has additional value in clarifying even more starkly the falseness of some alternate theories (hidden variables) that are still promoted from time to time.
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Does that mean that once the particles were synchronized, they remained synchronized even when moved apart? Like two gyroscopes once spinning on the same axis will remain at the same angle even when moved to different rooms?
Yes. To use an example, the particles are made to have the same spin (clockwise). The particles are moved apart 30 meters, then one of the particles is forced to spin in the opposite direction (anti-clockwise). The second particle, 30 meters away and spinning clockwise, instantly changes its spin to anti-clockwise. With the particles being far enough apart, the change could not happen due to another particle transmitting that change of spin information because the timing of the change is too quick. A ph
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This can't be it.
"To use an example, the particles are made to have the same spin (clockwise). The particles are moved apart 30 meters, then one of the particles is forced to spin in the opposite direction (anti-clockwise). The second particle, 30 meters away and spinning clockwise, instantly changes its spin to anti-clockwise. With the particles being far enough apart, the change could not happen due to another particle transmitting that change of spin information because the timing of the change is too qu
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See, if this was what was happening, you could transfer information faster than the speed of light. Which is definitely not what's being reported here. And also is impossible.
Yes, that is what is being reported here and elsewhere. This is the basis fo quantum entanglement. When you measure the state of one particle, the other particle instantly matches that measurement regardless of distance.
This article [caltech.edu] says to treat both particles as one which prevents the speed of light issue, but that's a cop out (in my
Re:What does that mean? (Score:5, Insightful)
>Yes, that is what is being reported here and elsewhere.
Bro, it is not.
You and I both have an enchanted box. If I put a red ball in the box, you see a blue ball instantly appear in yours. This can be used to transmit information instantly and superluminally. This magic on this box breaks a core rule of physics, and that's not what's happening.
You and I both have a different, more realistic enchanted box. If I open this box, I will see either a red ball or a blue ball. No one knows which one, but we DO know that if you open your box one nanosecond after I open mine, the rule is, if I saw a red ball, you see a blue one, and if I saw a blue ball, you see a red one.
This box doesn't break this particular law of physics. You might ask, hey, if it doesn't, how does your box tell mine to show a red ball faster than light? And the answer is, it probably doesn't. They were probably the same box, or two halves of the same object, in a quantum sense, and all that happened is that interaction snapped it into place. That's the type of thing these sorts of experiments ALWAYS show.
Because you can't actually transmit information faster than light with the second box. With the first box we could agree on a code and show balls (heh) at some rate, and send a message across the universe instantly. With the second box, we don't have anything going on like that, because even though I opened my box first, the fact that the ball was red (or blue) doesn't mean anything for you, because I didn't get to choose it.
Do you see the difference there? Is there any reason to assume that this is like the second magic box and not like the first? The first box transmits information faster than light, and is impossible. The second is how quantum entanglement resolves and doesn't actually transmit any information.
Re: What does that mean? (Score:1)
ãSthe fact that the ball was red (or blue) doesn't mean anything for you, because I didn't get to choose it.ã
What if you know that the other guy will do X if the ball is blue, and Y otherwise, and can you use foreknowledge to act on that information before he has a chance to?
Re: What does that mean? (Score:1)
Is it easier to steal the information in a classical letter, or entangled particles?
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Your second box isn't the best analogy of quantum entanglement as it's actually misleading you to the wrong conclusion. To extend the analogy, let's say the contents you see inside this enchanted box also depends on which side of the box you open up: if you open the top, it'll be either a red ball or a blue ball as you describe, but if you open the bottom, it'll be cubes, red or blue. What the other person with their "entangled" box will see when they open it will also depend on which side they open, as wel
Why isn't the ball transmitting information? (Score:2)
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isn't the ball effectively transmitting a random bit of information to both of you?
This is a contradiction in terms. A random bit conveys no information. Only non-random ones do. The question is meaningless.
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Again, in my opinion, that's a cop out, because claiming no information is passed between the two particles when measuring one which then tells you state the other, does not explain how the correlation happens.
It's really simple. God rolls a special pair of dice to select an outcome whenever a wave function collapses.
This article says to treat both particles as one which prevents the speed of light issue, but that's a cop out (in my opinion). Even if both particles are treated as one individual particle, and you change one particle which causes the other particle to match it, there is still the matter of distance. The change is instantaneous.
Distance and speed of light only mean anything for things propagating thru space. Nothing is traveling.
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The second particle, 30 meters away and spinning clockwise, instantly changes its spin to anti-clockwise.
You fell for the common entanglement confusion and implied false promise: Changing the spin of one does not change the spin of the other, you have simply broken their entanglement. Entanglement is read only, no writing, sorry.
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Well, I do not know whether this is true, but it would imply you cannot measure that spin. No information-transfer this way, remember? Alternatively, a whole lot of Physics theory goes out the window.
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I see some wannabe "moderator" is not conversant with basic modern physics.
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Yes. To use an example, the particles are made to have the same spin (clockwise). The particles are moved apart 30 meters, then one of the particles is forced to spin in the opposite direction (anti-clockwise). The second particle, 30 meters away and spinning clockwise, instantly changes its spin to anti-clockwise.
Nope. That would be transmission of information faster than light and it's not allowed by physics
Re: What does that mean? (Score:1)
What if I know that you will buy X at $Y if you see one result? Can I measure my particle first and since I know what you will do, buy X at $Y-1 to sell it to you?
Light says, hold my beer (Score:2)
248 km on fibre, across the entire universe in free space.
Your 30m is nice too though.
QE (Score:2)
I feel like this article is entangled with a previous article about 30 hours apart.
Practical question (Score:2)
Unfortunately its not easy to explain (Score:2)
So there is a set of measurements you can do to demonstrate that two states are entangled. (in a statistical average sense). You can do the measurements close enough in time that light could not travel from one particle to the other between the measurements. But it turns out (mo
This sounds neat (Score:2)
Now for a second team to verify by replicating the experiment
until then, they could claim they made FTL travel possible for all I care.
The benchmark should be "it has been verified", not "it was demonstrated".
Mars internet/communication (Score:1)
It really is the only way we are going to get lagless communication to a moon base or a colony on mars. I am sure this will be solved all the way soon.
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Never mind the moon or Mars, imagine instant communication right here on Earth without any wires, optical fiber or radio waves!
Only one chip necessary (Score:2)
For tens of thousands of qubits, however, we're almost certainly going to need so many chips that it gets difficult to keep them all in a single bit of cooling hardware.
Naah, we can just use Moore's Law to double the number of qubits on a chip every 18 months. If that doesn't work, we can use nano tech to make them even smaller!