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Quantum Entanglement Survives, Even Across an Event Horizon
StartsWithABang writes: One of the more puzzling phenomena in our quantum Universe is that of entanglement: two particles remain in mutually indeterminate states until one is measured, and then the other — even if it's across the Universe — is immediately known. In theory, this should be true even if one member of the pair falls into a black hole, although it's impossible to measure that. However, we can (and have) measured that for the laboratory analogue of black holes, known as "dumb holes," and the entanglement survives!
This should come as a surprise to exactly no one. Anyone who can apply logic can tell you that the physical universe is a layer above the non-physical energy (matter is merely 'bound energy') that is the fundamental substance of existence. Quantum particles are known to "flicker in and out of physical reality". That has been directly observed. So where do you think that energy goes when it's no longer *physically* present? Just disappears into nothingness, the one state that's simply not possible whatsoever? Of course it's still there, and of course the rules that apply to that non-physical energy still apply even when you can't physically access it. Energy is information, matter is merely a storage medium. The information is always extant, even if it's not currently represented on any physical storage medium.
A simple way to understand this is to visualize the universe as being made of numbers. The positive numbers can be represented by matter (regardless of polarity, so yes, anti-matter is positive numbers) and negative numbers cannot be represented physically, but are nonetheless just as 'real'.
Anyone who argues otherwise, yet agrees that 2 minus 5 equals negative 3, should be required to demonstrate physical proof that 2 minus 5 equals negative 3 before being allowed to speak further on the subject... ;)
Maybe this will help?
Can some physics types comment on the quality of the explanation.
https://www.youtube.com/watch?v=v657Ylwh-_k
1. No. The maximum speed is the speed of light in quantum mechanics. Entanglement doesn't even have a speed. It is, from all measurements that have been done, valid in any reference frame.
2. No. c is defined in terms of time, not the other way around.
3. No. The correlations from entanglement transfer zero bits of information. They can only be observed with the assistance of normal communication channels. Combining the two allows you to hide but not send data.
4. Obligatory xkcd: No.
What I think is the really important thing in the original paper is that information actually seems to be lost in the black hole. There is an enormous amount of theoretical musing about how to prevent information loss at event horizons (remember the black hole firewall?); this, if taken seriously, could have implications in quite a number of areas in theoretical physics.
To offer a simple explanation no it cannot send information faster than light. You can have these instant correlations but as the latest research actually shows, the values are truly random until measurement. So you can send these entangled photons and unpack one at one location and another at a second remote location and know you have the correlating bit but without knowing what that is, which must be sent classically, you have no idea what is being sent. Moreover currently i know of no experiment that preserves entanglement after measurement so you must also wait classically for the particles to arrive before taking the instant correlation measurement.
All science is based on statistics, you anonymous moron. There is always uncertainty in experiments and measurements because one can never be certain about anything - even the instruments used to measure observations have inherent uncertainties. Is the ruler you're using precise down to the atomic level? No! Can you be certain your instruments are perfectly calibrated?!?!? No!
This higgs was discovered with 6 sigma accuracy, which is more certain than the precision of manufacturing of most things you can purchase. It's the standard for declaring experimental certainty. If you're 99.9999998 % (which is what six sigma means) certain , there is literally a 0.0000002 % chance that the results were wrong. No one is going to bother to test beyond that, because the possibility of an error is so small it may as well be non-existent.
"The no-communication theorem states that, within the context of quantum mechanics, it is not possible to transmit classical bits of information by means of carefully prepared mixed or pure states, whether entangled or not."
See The No-Communication Theorem and the Einstein-Podolsky-Rosen Paradox.
Python: 'And then suddenly you have a language which says "we're all stuck with whatever the whiniest coder wants".'
For everything above quantum, the maximum speed is the speed of light.
No, for everything which can transmit information the fastest speed is the speed of light. If we find anything which can transmit information faster than light then time travel is immediately possible. You will know if this ever happens because the physicist who discovers it will get extremely rich winning lotteries.
If we send out a steady stream of entangled particles...we can send information quicker than the speed of light.
No - as witnessed by the the fact that we still rely on government grants to fund us and not winning the lottery. Quantum entanglement does not allow any information to be sent. It is like shining a very powerful laser pointer on the surface of the moon. The person on earth doing this could move the laser fast enough that it would appear that the bright dot on the moon's surface moved faster than light BUT the information flow is from the person on the earth to the moon and NOT from one point on the moon to another so there is no problem with relativity.
Quantum entanglement is the same sort of thing. You cannot use it to transmit any information faster than light. However unlike the laser on the moon it is very hard to come up with a believable explanation for the phenomenon which does not involve faster than light communication even if it will be impossible to use to transmit information.
This i understand this far.
So now, i have this black hole that i can't see. I send an object toward it. From my perspective, time slows to a halt on the sent objective at the event horizon, so it looks like it never enters. So it actually stays visible, right? Over time, the black hole would look like a big ball of stuff frozen in time? What am i missing here?
a) entanglement does not transfer information faster than light. Why? if i send entangled pairs of photons from a to b and c, and b and c detect these photons, the photons took time to reach b and c. If b does something to the photon, the entanglement is lost. If b and c measure they will know the state the other one received, however they can not influence what is received in the other place, so sorry guys, no FTL transmission of information
b) What is weird about entanglement is actually not so much it statistical property of the correlation. If a packs a white and black marble in two packages and mixes the packages and sends them out, the result from the viewpoint of b and c will be the same - each one will know which marble the other one received. The weird property is that the state is prepared in a way that the two possibilities are quantum states, which can be subject to phase shift, transitions etc, and are "collective" in that sense that b and c can transfer their state to particles (and possibly create further entanglement) - the basis for Quantum key distribution networks - and that the information which exists exists only in the form of a shared posteriori observation. i.e. the classical marble can be looked at without destroying the correlation, while a quantum entangled photon will be entangled with your measurement apparatus when looking at it.
c) what these guys did-AFAIU (my topic was very far away) is to create a model system of a black whole, which tries to represent a black whole in a way which we assume it is, observed some properties which can be predicted from this model (temperature of emitted radiation), and checked for some others - correlation, where they found correlation which they interpret as entanglment.
d) While did not look into the details, i can say from my own experience that such experiments are tricky, and i find the interpretation a little vague. But i have to look closer. I did use quantum state/operator tomography, which usually is the benchmark measurement when you want to prove entanglement, or properties of the superoperators describing your quantum operations. I understand that this may not be possible in this case, which is why one can go for other phenomenological approaches
e) One should be careful. Proving entanglement is not so simple (Look for entanglement measures), and proving that is actually *survives* the event horizon, instead of being created there, may be very nontrivial. It could very well be that non-entangled state are transformed in entangled states to some degree.
So I don't think they do anything funny ...
Let's test that with a joke... "Two neutrinos pass through a bar ..." - You're right: not funny.
It must have been something you assimilated. . . .
Quantum encryption protocol BB-84
You set up the experiment so that you can polarize a photon at 4 angles: 0, 45, 90 and 135 degrees ( | / - \ ).
There are two distant terminals, let's call them A and B, where the photons can be polarized and then checked whether they passed the polarizer or not. There's also a (dumb) source of entangled pairs in the middle, that sends one photon from the pair to each of the terminals.
Take a single (non-entangled) photon: If you polarize it at 0 degrees, it will pass the 0 degrees polarizer 100% of the time, 90 degrees 0% of the time, and the two diagonal ones 50% of the time. Extend to three other cases by rotating the initial polarizer by multiplies of 45 degrees; it's analogous.
Pass the same photon through three polarizers now: 0, 45 and 90 degrees. Unlike with just two (0 and 90) It will pass in 25% cases.
Take an entangled pair of photons. If you polarize one of them, the other behaves as if it was polarized the same as the first.
As entangled photons are sent, both A and B choose random orientations of their polarizers (each with own, locally generated random sequence); they write down the sequence: angle, result (photon passed or not).
Now the result is a string of zeros and ones each with an angle. If both randomly choose | or - then the result is valid, 1 means the other side had the same orientation, 0 means the other side had a perpendicular orientation. If one choose | or -, but the other choose \ or /, the result is random junk. The problem though is that neither of them knows which ones are right and which ones were faulty. There's a lot of data on both ends but none useful. No *actual* information was exchanged, because any that really did, was hidden behind the randomness of the polarizer setting.
Now, using normal, non-encrypted channels, A and B exchange the recorded random sequence of polarizer settings.
Each compares this with own recording and converts: Mine was |, their was |, got 1, record 1. Mine was |, their was -, got 0, record 1. Mine was -, their was -, got 1, record 1. Mine was |, their was / - discard record; it's junk.
And again, no information was passed from A to B because all the information was *generated*, in two copies at two ends. A couldn't send B a single bit. It's the dummy emitter that sent a random bit in two directions, and it was recorded on two ends. Still, to be actually read, it required normal subluminal exchange for decoding.
Nevertheless, both A and B now have the same sequence of bits, which they can use as a key for a common encryption - and they know the key had not been intercepted; no third party has it.
How do they know? Because for a third party to get any data from the photons, they'd need to put a polarizer along the way and since they don't know the sequence, they'd have to turn it at random.
Now remember the "three polarizers" case from the beginning?
"Mine was |, their was -, I got 1. Alarm! Somebody put a 45 degrees polarizer along the way! The communication has been intercepted!"
45 5F E1 04 22 CA 29 C4 93 3F 95 05 2B 79 2A B2