Satellite sets distance record for weird "spooky action" quantum communication


#1

Originally published at: http://boingboing.net/2017/06/19/satellite-sets-distance-record.html


#2

“spooky action”

Good name for a band.


#3

It is wrong to say “manipulating one affects the other.” If the two states could be divided up into a one and the other, then you would be doing some sort of FTL communication, or some spooky action at a distance. But this is not the case. There is only state - it is an entangled state.

Quantum states do not live in physical space. They live in a Hilbert space. Physical space is where the operators live, so you can say, there is an observable operator happening over in the satellite, and another one over in the lab – but since there is no communication of observable values, there’s no FTL.

It’s pretty subtle and it’s reasonable to have trouble digesting this, because it will sound like “the physicists are pulling a fast one with the definitions of ‘information’ and ‘communication’”, but it is very wrong to say that scientists do not understand this. The experiment is at a larger scale, but the result is absolutely what has been expected and thoroughly understood. Sure Einstein and Schroedinger had a little trouble with it, but Dirac didn’t, and by now any run-of-the-mill PhD should be able to explain this.


#4

Neat. I think this will be our future of communications, the ability to instantly transfer info over any distance. Great for when we goto the stars, but also useful on earth. And as long as there is network of these things, it should be able to reach anyone else on the network.

This would also explain why we aren’t picking up radio signals from aliens - they aren’t using communications that “leak”.


#5

Well, this won’t help because it doesn’t do that. It’s like doogly says; you can decohere entangled states from however far apart, but that doesn’t send information which is still limited to the speed of light.

Suppose I have a box with two cats, one black and one tabby. Without looking we separate them into two carriers, and fly those to different continents. Then you open yours and see it holds the tabby cat. That means you instantly know, despite the distance involved, that mine contains the black cat, right? Quantum entanglement is basically the same thing except using Schrödinger’s cats. Something changes far away, but there’s nothing you get to transmit.


#6


#7

you could agree to two different courses of actions based on the randomized results – maybe you a friend want to watch a short movie, but don’t know which :smiley_cat:

actually, that could be an interesting technique for influencing stock trading, battle plans, or other such things. you’d be able to coordinate behavior from afar, choosing from a pre-agreed-to set of equally valued possibilities.


#8

Also, reminds me of college.


#9

This scientific breakthrough is being hailed in China as a communications leap forward for the PLA (People’s Liberation Army), not a scientific achievement to be shared with the rest of the world. China has sent tens of thousands of aspiring scientists to study at the most prestigious universities in America and the West. The vast majority of Chinese graduate students socialize and live exclusively with other Chinese nationals, returning to China immediately upon completing advanced degrees or additional post-doctoral work at various U.S. research centers. This only lines the pockets of to top universities who rake in massive tuition fees from foreign nationals, while adding no value to the host state. What will it take for Western governments to realize that the CCP is only interested acquiring enough military power and technology to nullify NATO’s advantages?


#10

So that explains it. I feel much better now. What about a Macadamia space? Macadamias are smoother than Hilberts.


#11

I clarified. Thank you!


#12

it was also a good title for an album–


#13

Remember ‘Spooky Tooth”?


#14

http://www.spookytooth.sk/


#15

Quantum states do not live in physical space. They live in a Hilbert space. Physical space is where the operators live

What if one operator is at Pesco’s house and the other is on a spaceship traveling ludicrously fast? Would they agree on what happened and when?


#16

Three problems:

  1. This apparently won’t do that, as others have mentioned. But for the moment, let’s pretend it will.

  2. What “instantly” means is not absolute. Thanks to the relativity of simultaneity, you can have two events A & B (e.g., the sending and receipt of a message), and one observer could consider them simultaneous, a second could consider A to occur before B, and a third could consider B to occur before A – and they’d all be right.

  3. It then follows that you could send a message that from your perspective arrived instantly, but from the perspective of the recipient arrived before it was sent. In that case, you’d better hope like hell that the Novikov conjecture holds, because otherwise you’re in real danger of violating causality.


#17

It doesn’t transfer information, sad to say. If A and B are entangled, we can check to see what state A is in, and thereby know B’s state. But that doesn’t let the person looking at A send any information to the person looking at B. Which state which is in, is always random.

All the ways you can think of to send information don’t work. There is no way of looking at A that will tell you if B has or has not been looked at yet. There is no way to force A to be one thing and thus make B be the other. The act of looking at one of them disentangles it from the other, so you cannot look and then look again and stop looking when it acquires the value you want it to have.


#18

Given the persistence of perpetual motion machine proposals, this will not stop people still trying to do it for the next century.

I occasionally used to get people asking “so what if the Sun disappeared, would the Earth instantly cease to experience gravity” owing to the lack of understanding of what it means for the speed of light being an absolute limit for information transfer [the information in this case being that the Sun isn’t there any more]. I got tired of trying to explain it, and ended up saying “for the Sun to disappear that would violate the conservation laws, so it’s a meaningless question as it can’t occur in our universe.” Oddly, that tended to shut them up better.


#19

As others say, the nature of the entanglement is that it cannot be used to send a signal by itself. However, it may eventually be useful, and is necessary, for quantum encryption, which still requires a classical signal transmitted at or below the speed of light. Quantum encryption will become important with the advent of even fairly simple quantum computers since Shor’s algorithm is among the simpler quantum algorithms and RSA cannot realistically resist being cracked by it. This is the main reason industry and governments pump money into quantum cryptography and quantum encryption (and why I have a job).

However, quantum computers will be able to do so much more than break public key cryptography. They’re not replacements for classical computers, but they can solve certain kinds of problems that would take classical computers an impractical amount of time no matter how powerful you could make them (and the theoretical limits on how powerful a classical computer can be are pretty well understood, even though engineering is a long way from reaching it). This means, in effect, that a classical computer with a quantum co-processor would be useful for running some programs that would’d take any classical computer alone longer than the lifetime of the universe.

I really don’t like the term quantum internet as it often conjures up misconceptions. But such quantum-capable computers linked with quantum encrypted channels would be the logical end result of these two closely related fields, and there’s probably no stopping the press from calling it the quantum internet :confounded:

Note that you’re not going to suddenly see a tectonic shift in computing. For one thing, some of the more interesting algorithms will require more powerful quantum computers than the circuit needed to run Shor’s algorithm, and will consequently be much harder to learn to build because the biggest pain in the ass in QC, the decoherence problem, gets worse with scale. And also because what you see as an end user is based as much on the software ecophere and the ways in which companies and developers shape user experience, as it is on what goes on under the hood. Markets take decades to comprehensively exploit new technologies.


#20

Wouldn’t it mean that instead of a wave function of probabilities, particles actually have some deterministic property that is revealed when you run the entanglement experiment?

Where is my Nobel prize?

– Internet commentator