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!

Comments

No shit, Sherlock

[Anonymous Coward]

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... ;)

Re:No shit, Sherlock

[Anonymous Coward]

Mathematics is not your strong suit, is it?

Re:No shit, Sherlock

[Anonymous Coward]

Two ocean waves with exactly counter energy meet in the middle of the ocean and cancel each other out. Where did the waves go? They "flickered out of physical reality".

Re:No shit, Sherlock

[khallow]

In reality, ocean waves don't do that. Instead, they pass through each other. If energy were somehow canceling itself out on Earth, we would have noticed by now. In particular, if ocean waves were readily canceling each other's energy out, then we would have a vastly slower rotating Earth due to the loss of energy through such wave action.

Re:No shit, Sherlock

[interval1066]

wtf are you talking about? You remind me of a numbers nut job that crank Noory was interviewing on coast to coast am. After a few minutes of her blathering even George was going "Huh"?

Re:No shit, Sherlock

[Anonymous Coward]

Wait, can you explain it in terms of a flock of sparrows?

Re:No shit, Sherlock

[Anonymous Coward]

In reality, ocean waves don't do that. Instead, they pass through each other. If energy were somehow canceling itself out on Earth, we would have noticed by now. In particular, if ocean waves were readily canceling each other's energy out, then we would have a vastly slower rotating Earth due to the loss of energy through such wave action.

This is complete utter BS. Waves cancel each other out all the time. Look up interference patterns and wave propagation on Wikipedia.

Re:No shit, Sherlock

[khallow]

This is complete utter BS. Waves cancel each other out all the time. Look up interference patterns and wave propagation on Wikipedia.

Yes, let's look at those things. The first thing we notice when we look at wave propagation is that energy is conserved which in itself is completely at odds with your assertion that waves can cancel themselves.

When we look at interference patterns (which occur when waves interact at best weakly with each other), we see not only local cancellation, but also local reinforcement. When there are regions where waves subtract from each others' amplitude, this process also results in regions where the waves add to each others' amplitude. Thus, energy is conserved.

Re:Dumb Holes?

[h33t l4x0r]

Hey come on, let's give Donald Trump and Ben Carson a break, they've been through a lot lately.

So.. for a non-physicist

[bytesex]

- For everything above quantum, the maximum speed is the speed of light.
- This dictates cause and effect, and therefore time.
- If we send out a steady stream of entangled particles, and sometimes change and sometimes don't (at the one end), and measure at the other (this is how I imagine how a bitstream would work using quantum entanglement, correct me if I'm wrong), we can send information quicker than the speed of light.
- Therefore the information goes back in time.

Or something?

Re:So.. for a non-physicist

[cpuffer_hammer]

Maybe this will help?
Can some physics types comment on the quality of the explanation.
https://www.youtube.com/watch?v=v657Ylwh-_k

Re:So.. for a non-physicist

[Anonymous Coward]

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.

Re:So.. for a non-physicist

[Anonymous Coward]

"hide but not send data"

I meant that you cannot send more data than you could with the classical communication channel, just to be clear.

Re:So.. for a non-physicist

[h33t l4x0r]

So tachyons or neutrinos are "below quantum"? If so, what does it mean to be below quantum?

Re:So.. for a non-physicist

[Anonymous Coward]

> - If we send out a steady stream of entangled particles, and sometimes change and sometimes don't (at the one end), and measure at the other, we can send information quicker than the speed of light.

Yes. I think this simply implies that you can't take a particle and measure whether it's in collapsed state or not. Because if you could, then yes, just like you said.

Re:So.. for a non-physicist

[Anonymous Coward]

If A and B are entangled, and you measure A, then you know what state B is in. You can't manipulate A in a way that causes B to collapse into a particular state, so you can't use it to send information.

Lets say there's some parent particle, P, with a total spin of 0. It decays into 2 photons. Photons have spin of +- 1, so you know that A and B each have +1 or -1 spin. Angular momentum is conserved, so you know that spin(A) + spin(B) = 0.

You measure A and get -1, so you know that B must have a spin of +1. That's all that entanglement means.

The only weird part of quantum mechanics that factors into this is that spin(A) wasn't -1 before you measured, it was some superposition of +1 and -1. When you measure A, you become entangled with A too, and the superposition collapses into 1 state or another. The universe is a lazy fuck and doesn't keep track of the full state of A and B until it's needed for something.

Re: So.. for a non-physicist

[mSparks43]

And this is where you always lose me.

Nothing here proves it wasn't -1 the whole time.

Re: So.. for a non-physicist

[Anonymous Coward]

There's a measurable difference.

Re:So.. for a non-physicist

[del_diablo]

>- Therefore the information goes back in time.
How and why did you get to that conclusion? There is a giant leap of logic here, and I want to explained

Re:So.. for a non-physicist

[burtosis]

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.

Re: So.. for a non-physicist

[umghhh]

The beauty of this whole theory is that before you measure it, you do not know. If you measure it you know. So the whole problem what value it has before you measure it is moot but after you measure it, you even know more than you would expected because the fuckers are entangled.

Re:So.. for a non-physicist

[Anon-Admin]

There is something I have not seen an answer for.

If you measure it and get a -1 but do not write it down and do not tell anyone. Then you are the only one that knows the state.

If I come in after you and measure it, will I get a -1 or is there a chance of me getting a 1?

So I guess the question is, does the particle exist in a superposition when not being observed and return to that superposition after observation, does the particle exist in a superposition until observed then lock into a position, or has it always been in that position and we just did not know it until observation?

Re:So.. for a non-physicist

[Anonymous Coward]

Wigner's friend.

Re:So.. for a non-physicist

[Blaskowicz]

Neutrinos are particular with mass that go slower than light, although the mass is like 0.000000(...)00001 and the speed like 99.999999(...)9 % the speed of light.

So I don't think they do anything funny ; neutrinos merely go faster than light when that light goes through a non-vacuum medium, like beta radiation that makes a nuclear reactor glow blue in the swimming pool.

Re:So.. for a non-physicist

[Anonymous Coward]

nope, you may be sending data instantaneously, but information must be observed, and that occurs below the speed of light.
In physics, if you find yourself discovering a new theory that violates the basic laws, reconsider your theory first.

Re:So.. for a non-physicist

[JaredOfEuropa]

Re point 4: my understanding of current theory was that if you can send information faster than light, then it is possible to send information back in time.

Re:So.. for a non-physicist

[Anonymous Coward]

- If we send out a steady stream of entangled particles, and sometimes change and sometimes don't (at the one end), and measure at the other (this is how I imagine how a bitstream would work using quantum entanglement, correct me if I'm wrong), we can send information quicker than the speed of light.

I don't know where you get that from.

If you have two particles in your hand, you have to send one of them to "the other end"
How do you plan to do this faster than the speed of light?

If you pack one particle up in your car and drive it there, it clearly isn't going faster than the speed of light. Even packing it up in your spaceship will be slower than the speed of light.

Also where do you get "sending information" from as well?

If I slice a coin in half long ways and seal both parts in an envelope, one of which I keep and one of which you keep and take with you to "the other end", just because later on we open the envelopes and you find you have the "heads" slice allows you to infer I must clearly have the "tails" slice.

I fail to see how you believe information was sent in any way, let alone above or below a certain speed...

Re:So.. for a non-physicist

[interval1066]

No.

"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.

Re: So.. for a non-physicist

[mSparks43]

If bob or Alice leave for the shop.

When you measure if it was bob or Alice that left for the shop.

You know if Alice or bob didn't leave for the shop.

There is nothing magical or even that interesting happening here.

Re:So.. for a non-physicist

[Anonymous Coward]

If we send out a steady stream of entangled particles, and sometimes change and sometimes don't (at the one end)

That's the classic error people make when pondering about this: you cannot "change" anything at either end. You can only do a measurement, and the result of the measurements on either side will be completely random. But when you compare the results of those measurements with each other, they will be correlated (i.e. matching for some percentage).

For example, by changing your detector to horizontal polarization, you won't be forcing photons to be horizontally polarized. You will just measure that on average, 50% of the photons will not make it through te filter. But which one is completely random, and not controllable by your setting of the detector.

Re:So.. for a non-physicist

[Anonymous Coward]

There is nothing technically wrong with the youtube explanation, but it seems to be overly confusing. A lot of juggling with X, Y and D, and it's not very clear what exactly they're trying to explain in the first half hour.

To explain Bell's Theorem, I prefer the following: http://quantumtantra.com/bell2... .

Re: So.. for a non-physicist

[Anonymous Coward]

How fast are you sending your stream of particles ?

Re:So.. for a non-physicist

[Anonymous Coward]

You are correct but some clarification is needed. Any faster-than light effect is backwards in time in some valid reference frame, so as far as that is concerned you are correct. For two observers who are stationary relative to one another and in a flat spacetime, sending something faster than light does not however imply that it is sent backwards in time from either point of view. (Only if you assume that you can send information backwards in time directly, but that is a stronger assumption.) If their relative speed is high enough it is possible that one observer may send a message at some v > c, which the other then sends back so that it arrives at the starting point before it was sent. This arises because "some valid reference frame" I referred to above means one moving with sufficient relative velocity.

All of this can be derived directly from the basic assumptions of Special Relativity so I would write it up as "almost irrefutable" rather than just current theory. If you are not very familiar with spacetime diagrams, I recommend drawing this as a good exercise. Try to start the two observers at different distances and relative velocities (including direction) and see how it varies.

Point 4 is invalid simply because the assumptions are invalid, as you correctly said. I could arguably have put the comic link next to either point 3 or 4.

Re:So.. for a non-physicist

[colinrichardday]

If you send information faster than light, then the information is going backwards in time wwith respect to some reference frame.

Re: So.. for a non-physicist

[Anonymous Coward]

And this is where you always lose me.

Nothing here proves it wasn't -1 the whole time.

If you have a process that emits two electrons of opposite spin, you can set it up such that the spins are vertical and opposite. So when you measure, one is up, and one will be down. However, spins can be aligned or measured in any 2D direction, so you can setup the measurement apparatus to look for left and right spins. If one particle is in an up state, and you do so, you have a 50-50 chance of getting left or right. If the other particle is down, you also have a 50-50 chance of getting left or right, and it is independent... so there is a 25% chance you will measure two lefts and a 25% chance of two rights. However, if both particles are in a state superposition of up&down with down&up, you never see the two lefts and two rights because system state constrained in a different way.

This is a specific case of something like Bell's inequality which another poster linked to above, and there are many situations where this comes up. Either the particles were not in their specific state before being measured, or you need some sort of determinism such that the universe was setup in such away that your measurements and everything was determined before the start of the experiment.

Re: So.. for a non-physicist

[mSparks43]

Don't see how that answers anything.

what is so special about having some set
[A,B]

dividing them.

then measuring one of them, determining it is say A
And implying the other is B.

And, why, when the most interesting bit of all this is the superconductors.
Are we not discussing them.

Re: So.. for a non-physicist

[mSparks43]

But this is just set theory.

Why is it a "miracle" that if you throw one element of a set into a black hole, that doesn't affect the other elements of the set.

Re:So.. for a non-physicist

[fahrbot-bot]

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.

Re:So.. for a non-physicist

[RubberDogBone]

It would go back in time only from the perspective of an outside observer. From the perspective of the particle itself, it is still in what it would perceive to be normal time, if a particle could perceive such a thing.

Re: So.. for a non-physicist

[Anonymous Coward]

Ok. That's about Quantum. What about SPECTRE?

Re: So.. for a non-physicist

[Anonymous Coward]

What do you mean this is just set theory? If you mean it is just two objects from a single set with predetermined values, then you're just wrong and didn't understand the example. If you're saying it is just set theory in the sense that you have two possiblitilies |ud> and |du> (using bra-ket notation), then yeah, the math is really simple for anyone who knows basic calc and can pick up some extra notation. The internet and popsci makes entanglement way more complicated than it is because they try to avoid the math when the math is really simple.

Re:So.. for a non-physicist

[Anonymous Coward]

If you are saying that the average value approximately equals the expected value, isn't that a way of sending information faster than light?
For example, for every bit of information I read the state 100k times to get the average value and determine it's a 0 or a 1, and continue on for each bit of information.
If the distance is covered is 1 light year, that's a trivial amount of work to send data FTL.
I am probably misunderstanding but would be interested in a rebuttal. Thanks.

Re: So.. for a non-physicist

[mSparks43]

what else is
-> you can set it up such that the spins are vertical and opposite

Other than
"two objects from a single set with predetermined values"

So yes, If it means something different I don't understand the example. which is why I started with "and this is where you lose me everytime".

Re: So.. for a non-physicist

[Anonymous Coward]

The spins that were vertical and opposite were set theory, but the second thing he suggested, with state superposition, were non-set-theory.

The set-theory one can get two lefts or two rights from a left/right detector, but the entanglement one cannot. That's the difference.

BTW, I found this to be a decent explanation about why "superdeterminism" (which is a potential loophole in Bell's Inequality) is considered an unacceptable: http://philosophy.stackexchang.... It basically means the world is deterministic in such as way that we will only decide to look at things when the results will look nondeterministic.

As a *very* rough analogy, like saying that one kid is reciting the alphabet, but always getting exactly 1 letter wrong at random (replacing it with "orange"), and the teacher is always listening to 25 of the 26 letters, and no matter how many times you repeat the experiment the teacher will always choose to fail to listen to the single wrong letter. This continues to occur even if the recital is recorded and the teacher replays it on a different day. Conceivable but kind of like a conspiracy theory about the universe.

Re: So.. for a non-physicist

[mSparks43]

->but the second thing he suggested, with state superposition, were non-set-theory.
Why.

We're mostly talking about electrons in a superconductor as far as I can tell.

And the "infinities" that produces is ALL set theory.

Re: So.. for a non-physicist

[Anonymous Coward]

(Heads up, there are at least two different ACs now, I'm not the one that you just immediately replied to, but wrote some earlier posts)

We're mostly talking about electrons in a superconductor as far as I can tell.

No, this can be simple free flying electrons or atoms through a Stern-Gerlach experiment or something similar. It is pretty simple setup, without any of the mess of talking about electrons in a sea of other particles like in a superconductor. You just have something with a quantized spin, and for any angle measurement there are only two possible measurements.

And the "infinities" that produces is ALL set theory.

There are no infinities involved at all. It is just a couple binomial operations. If you have a up spin-1/2 particle and a separate down spin-1/2 particle, putting them each into a device measuring the horizontal component of spin will give two independent, 50-50 events. You get a table of probabilities that same as you would for the different combinations of flipping two coins. An entanglement that produces a superposition of the system states of up&down with down&up will not produce this table, as the measurements of the two particles is no longer independent. You have a 50-50 chance of getting left&right or right&left.

If you understand things like set theory (not really that relevant though), basic calculus and some idea of vectors, you can just learn Bell's theorem the proper way with the math. It is very straightforward, something usually taught to second year undergraduate physics students. Then you don't have to deal with random people on Slashdot half remembering it, or trying to superficially dumb it down into words, which actually makes it more complicated.

If you can get as far as seeing that some of these operations are just simple vector projections, then you can start to see a wide variety of operations and things that can be done to the superposition state that can't otherwise. You can project the |ud>+|du> state onto different bases in succession, and maintain the correlation, when for predetermined individual particle states, the first projection would destroy correlation.

Re:So.. for a non-physicist

[SharpFang]

The misconception comes from:

"Pack your particle in your car and send it there, no information is known still. Now measure the particle at your end and at the other end simultaneously. You'll get the same result instantly".

The problem is this doesn't really transmit information. You could get two sealed envelopes, put two identical cards, either with "1"s on them or with "0"s, one in each, then deliver one to the distant place. If two people now simultaneously open the envelopes, "the information about the number on the card will be transmitted instantly".

And one person may choose not to open the envelope.

No, no useful information was transmitted. The one who opened the envelope can't tell whether the other person opened the envelope by color of the marble alone. In this scenario the quantum entanglement boils down to the "hidden variables" theory and doesn't provide anything better than completely standard communication.

Take a different scenario.

The cards are written in special inks that require specific chemical to become visible. Specifically, you have one kind of ink in which you write "0" or "1" and another, in which you write "A" or "B". You have swabs of cotton with two chemicals - one will make the "0" or "1" to show up - but will simultaneously wash out the "A" or "B" unrecoverably. The other will do the opposite, washing the "0/1" off but showing the "A" or "B".

You prepare identical pairs of the cards - both cards of the pair have the same number and the same letter. You distribute the cards to the two parties, and each can choose a swab at random, to display either a number or a letter.

Later they compare notes, which swabs they used - if they both used the same type of swab, they know they got the same number, or the same letter. If they used different swabs - they just agree to disregard the number-letter pair. They also share some of the results.

If a third party wants to intercept it, they can read the number or the letter, but if they choose a number, they'll never know the letter and vice versa. They can create a fake card which contains the same number or the same letter, but not both for sure - they got a card and found it to be "1", so they can create a card with "1" but put "A" or "B" randomly.

Now if the two parties compare their partial results, find that both checked for a letter on a particular card, and one got "A" while the other got "B" that means someone faked one of the card and the channel was compromised.

That's quantum encryption. A useful exchange was made, and it was absolutely taper-proof (or taper-evident if you prefer), but no superluminal communication occurred - actually no communication occurred over the quantum channel; simply both parties obtained *some* common information; later standard communication allowing them to verify whether there were any superfluous measurements.

Re: So.. for a non-physicist

[mSparks43]

Pretty sure all this requires interactions with super conductors at some point.

That's how dwave is doing it anyway.

Re: So.. for a non-physicist

[Anonymous Coward]

I am not a physicist, but I think it is more complicated than that. The interesting case occurs if A and B measure spin with detectors that are offset 45 degrees. If they were simply measuring a pre-existing phenomenon, the correlation (or better anti-correlation) of results should be 0,5. However, it is 1/sqrt(2)=0,707... This cannot be explained with any prior attribute of the measured particles themselves.

Although I may have understood it completely wrong ...

Re: So.. for a non-physicist

[Anonymous Coward]

You were linked directly to an example that involves no superconductors at all. And there are a lot more others, as a large amount of such research is done with things like atoms in traps or entangled photons. If you want to keep being pretty sure about such things, that would amount to being delusional.

Re: So.. for a non-physicist

[mSparks43]

What link would that be?
Stack exchange linking to Wikipedia doesn't count for much with this stuff imo.

And that's the only link I see in this thread.

Any experiment running close to absolute zero is using superconductivity. All these experiments, photons or electrons are currently using super cooled materials as far as I've seen.

Re:So.. for a non-physicist

[david_thornley]

That is correct if Special Relativity holds. Now, I'm as positive that it holds as I am about any scientific theory, but it still could be wrong.

If we toss Special Relativity and have a preferred inertial reference frame, then FTL does not mean backwards in time.

If you have Special Relativity and FTL, you've got time travel, or at least the potential of such.

Re: So.. for a non-physicist

[Anonymous Coward]

The Stern-Gerlach experiment was explicitly named.

Any experiment running close to absolute zero is using superconductivity

No, this is not true at all as only certain materials will transition in to superconductivity.

All these experiments, photons or electrons are currently using super cooled materials as far as I've seen.

Experiments involving electrons or photons travelling through free space aren't involving materials, super cooled or not.

Re:So.. for a non-physicist

[lucien86]

"Re point 4: my understanding of current theory was that if you can send information faster than light, then it is possible to send information back in time."

That would only be correct if General Relativity remains correct at FTL speeds, and there's more empirical proof for Leprechauns or homeopathy than there is for that.. A much simpler FTL model is that time is point like and not a dimension, and that dimensional time is just a delusion - an abstraction.. As for dilation and space like time they can be explained by treating speed as a component of velocity. For an object moving in a straight line its velocity forms a line that behaves like a dimension local to the object..

Re:So.. for a non-physicist

[lucien86]

You threw that in there.. The very definition of the unanswerable question. What is the nature of the observer paradox? Answering that question can take you down some very pretty rabbit holes. The answer that the consciousness does collapse the wave function would be pretty irrefutable evidence that some 'psychic' model of the universe is correct.. There are two obvious alternatives - a physical mechanism in the observers brain, or in the process and instrumentation of the observation itself.
What we are looking for is the ultimate smoking gun for the superposition breaker - and ultimately the most likely probable answer is very simple, it is quantum noise that breaks the superposition. In fact this is really the opposite to the described experiment - quantum noise gets in and destroys the superposition the moment the box is open.
In the real universe Schrodinger boxes themselves are actually virtually impossible to build anyway, the walls of the box are essentially virtually identical to the event horizon of a black hole. But even event horizons cannot stop gravity and gravity carries information about mass and energy. As the joke goes you can choose two - general relativity, black holes, or the conservation of momentum..

Re: So.. for a non-physicist

[mSparks43]

->No, this is not true at all as only certain materials will transition in to superconductivity.

At absolute zero all conductors are super conductors.

some materials transition at higher temperatures.

The "useful" super conductors are the ones that transition above the boiling point on liquid nitrogen.

->Experiments involving electrons or photons travelling

But they are "entangled" in a super conductor first.
https://en.wikipedia.org/wiki/...

"As I understand it"

->Stern-Gerlach experiment
Does that have Quantum entanglement?
Don't think it does.

Re:So.. for a non-physicist

[Anonymous Coward]

Really, please go take a couple of actual classes in GR.

You don't understand it, or you would not be saying anything about "speeds", even casually, let alone talking about FTL as if GR does not admit a democracy of causal cones. There are several exact solutions to the EFEs that admit tacyhons, and you can even get decent behaviour out of spacetimes where tachyons and fields that feel non-gravitational long range force do not interact non-gravitationally. (In fact, that restriction does not arise from GR itself but rather from gauge theories describing the non-gravitational field content.)

Once you go to numerical relativity or other approximate solutions to the EFEs, you can come up with arrangements of tachyons that can mimic other field content (this has even been done for the dark sector, by e.g. C Schwartz @ UC Berkeley and J.K. Kowalczynski @ IFPAN), however the group theories for such approaches are, well, byzantine.

Indeed, one of the great advantages of GR is that it can be used to study things that violently disagree with SR.

All one has to do is abandon the *convention* that in the limit where spacetime regions are very small, test particles obey the Poincare group. You still get lots of leeway -- not everything is a test particle! (You also then have to be careful about the interpretation of quantum field content in such a setting. What you gain from admitting that not everything is a test particle is very close to abandoning any sort of agreement on particle count between different observers. OTOH, semiclassical gravity works well, even though it has exactly that mindbender in it.)

Finally, 4-velocity in General Relativity is almost always normalized to -1, +1, or 0, depending on sign convention and whether the geodesic is timelike, spacelike or null for the causal cone under consideration (the slope of which is conveniently set out by "c", which need not be the same "c" as in Special Relativity). "Faster than light" has a 4-velocity of +1 given the usual sign convention and c based on light, for any curve that parallel transports its own tangent vector (e.g. any geodesic). "Slower than light" has a velocity of -1. And this is why one regularly sees the use of geometrized units where c=1. (Indeed, in a vacuum solution, with no non-gravitational content, we don't even care to consider any other possible value of c, and we don't care about how c relates to non-present field excitations or classical objects. There are *plenty* of vacuum solutions that have been and are useful for making concrete (and even accurate) predictions about observations of parts of the universe.).

Everything else in your post is simply word salad. I don't know what you hope to accomplish.

Re: So.. for a non-physicist

[Anonymous Coward]

At absolute zero all conductors are super conductors.

No, there are a variety of states, and typically fermions and bosons act differently at absolute zero. Helium-4 becomes a superfluid, it doesn't become a superconductor. Some materials even become perfect insulators.

https://en.wikipedia.org/wiki/... [wikipedia.org]

In most situations Cooper pairs have nothing to do with entanglement. There are a large number of experiments that involve entanglement without superconductors.

Does that have Quantum entanglement? Don't think it does.

Doesn't matter what you think... anything that involves decay into two particles and is preserving things like angular momentum will produce entangled particles. Undergrad labs use a simple beam splitter and single photon source. There is plenty of discussion of variations of the Stern-Gerlach experiment used to study entanglement. Heck, the original test of Bell's inequality didn't use superconductivity, and you can find a long list of other such experiments on Wikipedia, or in an actual textbook.

Re: So.. for a non-physicist

[mSparks43]

Pretty sure that fermions , bosons and helium-4 aren't conductors.

As I understand the Stern-Gerlach it shows you entanglement exists, it doesn't give a set of entangled things you can experiment on that we have been discussing so far. Even your link to the "original test" says nothing about the photon source.

Further more, I don't see any of this actually explaining anything, other than reinforcing what I said ealier, in that the "CHSH inequality" IS a set experiment, testing set theory (and crudely at that).

Re: So.. for a non-physicist

[Anonymous Coward]

Pretty sure that fermions , bosons and helium-4 aren't conductors.

All conductors are fermions or bosons, and not all conductors form superconductors as seen in some of the coldest states achieved with sodium and rhubidium, or even simple alloys in the case of the Kondo effect... and you said

Any experiment running close to absolute zero is using superconductivity.

Which contains so much wrong, because as pointed out other states near absolute zero, and this is irrelevant for a large number (and probably actual majority) of experiments involving entanglement.

As I understand the Stern-Gerlach it shows you entanglement exists,

You can find intro level text freely available that describe how it generates entanglement.

Even your link to the "original test" says nothing about the photon source.

They used an atomic cascade in the original experiment. But there are lots of off the shelf entangled photon sources... as already stated and the point was that it is done with photons which involves simple optics and no supercooled components. SPDC components are off the shelf now and used in undergrad labs.

At this point, either your trolling, or you have so much confidence in your vague superficial impressions of things that you don't seem to be actually reading or looking up anything. I don't think there is any point in continuing this, but for anyone else who stumbles upon this, they can see the links to things that were easy to find and hopefully realize that answers/corrections are easy enough to find for anyone with reading comprehension.

Re: So.. for a non-physicist

[mSparks43]

So maybe we consider "superconductivity" differently.

Your text says:
3.1. The free particle
Now we consider a free, spin-1/2 particle. The Hamiltonian consists only of translational kinetic energy

Are you saying that is achievable in a material with resistance?

According to the one that left

[Anonymous Coward]

the other particle never fell in. It takes infinite time to reach the event horizon for a particle falling in, from the perspective of an outside observer, which that entangled particle is.

So I'm not finding any particular "Wow" moment hearing that entanglement is still possible.

Re:According to the one that left

[Anonymous Coward]

the other particle never fell in. It takes infinite time to reach the event horizon for a particle falling in, from the perspective of an outside observer, which that entangled particle is.

So I'm not finding any particular "Wow" moment hearing that entanglement is still possible.

This is like the concept of how Hawking radiation comes about, but applied to quantum entanglement.

The important bit here is that information is not lost when it crosses the event horizon of a blackhole.

This is coming from a Stanford PHD.

Re:According to the one that left

[NoZart]

This particular thing about event horizons always bugs me (i am no scientist at all): If the stuff falling in never enters from an outside perspective, shouldn't black holes look like Katamari balls and be quite visible?

Re:According to the one that left

[Yosho]

Think about how vision actually works; photons emitted from a light source bounce off of an object and enter your eye. Your eye detects the photons, and your brain constructs an image of them based on their wavelength and direction of arrival.

You can't see a black hole because its gravitational field is strong enough that even light can't escape. Since no photons are bouncing off, there's literally no way that your eye can perceive it.

Re:According to the one that left

[NoZart]

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?

Re:According to the one that left

[mbone]

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?

The red shift. Drop a flashlight down into a black hole (you'l need a big black hole so that tidal forces don't destroy the light on the way in). As it falls, the red shift increases rapidly and so the flashlight both reddens and dims rapidly. (That is, fewer photons per second AND each photon has lower energy.) After a short time near the event horizon, you will receive the last photon you will ever get from the flashlight - and the same is true no matter how bright the light. So, no, it is no longer visible as it falls in.

Re:According to the one that left

[NoZart]

Thanks. All those "popular" explanations always only go so far as to exclaim "time slows for the object, so you never see it enter the event horizon" which misses this crucial info :)

Re:According to the one that left

[Mass Overkiller]

THANK YOU for that explanation I was wondering the same thing for ever. That really helped thank you!

Re:According to the one that left

[Anonymous Coward]

You can't see photons bounce off the event horizon (and the Hawking radiation would be way too low for the eye to see except for possibly a very small, microscopic black hole). However if you have a large light source, you will definitely see the black hole is there, as there will be plenty of photons that bend around the black hole, even coming right back at you if you are holding the light source.

This is something that may be actually tested within the next decade or two with the Event Horizon Telescope, which will possibly resolve the event horizon of Sagittarius A*, and looking at how the light bends around it will tell you the size and spin of the black hole.

Re:According to the one that left

[HiThere]

This particular thing about event horizons always bugs me (i am no scientist at all): If the stuff falling in never enters from an outside perspective, shouldn't black holes look like Katamari balls and be quite visible?

No. As things approach the event horizon the light from them is increasingly red-shifted, so that by the time they actually reach the event horizon it's been red shifted down to 0 hertz. Also, the light almost goes into orbit, so it needs to make an ever increasing number of orbital passes to escape to where you can see it, so eventually it takes it forever to get there. Both effects are happening at the same time.

Please note that this is an idealized scenario, and assumes perfect vacuum between you and the event horizon. In actuality there would be enough stuff to absorb the light before it reached you. It's possible that even virtual particles would suffice to absorb the light before it reached you as the end-point was approached.

Re:According to the one that left

[Anonymous Coward]

Gravitational redshifting still reduces the photon wavelength from UV to Vis to IR to Microwave to Radio to black.

Re:Dumb Holes?

[h33t l4x0r]

Ouch, A downvote! Let's be fair though. Carson and Trump are clearly quantumly entangled because once a voter realizes one of them is full of sh*t they immediately know the other one is as well. It's science!

Unsurprising

[Anonymous Coward]

Neat, but unsurprising. Information can't escape from black holes, but quantum entanglement collapsing does not transfer any information from one particle to the other. So this really is the result you'd expect.

finally!

[Gravis Zero]

Bob finally has an excuse to throw that cheating bitch, Alice into a black hole: science!

Re:finally!

[mbone]

Eve will cackle with joy.

Re:finally!

[wonkey_monkey]

While Claire and Dave are, as usual, left out entirely.

more we discover, more we realize we know nothing

[sittingnut]

with each discovery in quantum physics and astronomy, we discover we don't know anything about far greater part of the universe(or universes) and how it(they) work, from dark energy and matter, to variety of quantum effects.

In MWI, this is obvious

[SilentTristero]

In the many-worlds interpretation of QM, also called "QM without collapse", becoming more and more mainstream, this is a straightforward consequence of entanglement. When you measure the spin or polarization of your entangled particle, you become entangled with it, so in a sense all you're doing is discovering which "universe" you're in. And of course that universe is correlated with the corresponding other particle, no matter where it is now.

Re: In MWI, this is obvious

[Anonymous Coward]

It's also easily explained in the Possibilist Transactional Interpretation. Emission happens before the event horizon is crossed by the offer wave, absorbtion after. Energy is transfered directly between these points in spacetine. Entaglement happens prior to emission so one transaction instantly impacts the other.

Re:In MWI, this is obvious

[Oligonicella]

I discover which universe I'm in simply by reading the brand, title and issue number of the comic.

Re:In MWI, this is obvious

[HiThere]

I prefer the many-worlds interpretation also, but I think it's a mistake to say it's "becoming more mainstream". It was originally published by (among others) J. Archibald Wheeler, and you can't get much more mainstream.

For that matter there are several valid interpretations of Quantum Mechanics, and it's probably a mistake to choose between them. There's even merit to the Copenhagen interpretation ("Don't try to understand it, just calculate.") Until there's an experimental way to choose between the interpretations, you just need to accept them all as somehow saying things that are, as far as we can tell, the same, even though their translations into, e.g., English seem totally different.

Re:In MWI, this is obvious

[SilentTristero]

Re: "becoming" mainstream, don't think it's there yet: I think something over 50% of practicing physicists accept it as of a few years ago, which is a change from even a decade ago. As for other interpretations, experiments like this one are making the CI much harder to swallow - instantaneous collapse? Really? FTL signaling?

Besides, Copenhagen is just a worse explanatory framework. If we're going to make any progress on quantum computation, thinking about what's _really_ going on rather than about mysterious shadows and collapse keeps things simple, local, and deterministic (in the multiversal sense of course) But you're right that something like Cramer's Transactional Interpretation could be the cause rather than multiple worlds. I just find it hard to stomach the idea of "backward causation".

Re:In MWI, this is obvious

[WaffleMonster]

In the many-worlds interpretation of QM, also called "QM without collapse", becoming more and more mainstream, this is a straightforward consequence of entanglement.

The most outlandish explanations usually are the most straightforward once their assumptions have been discounted.

Re:In MWI, this is obvious

[SilentTristero]

Indeed. But I'd argue Copenhagen is the one with the outlandish assumption here (instantaneous collapse on "measurement").

Re:In MWI, this is obvious

[HiThere]

http://phys.org/news/2015-11-n... 404 error, page cannot be found.

Re:In MWI, this is obvious

[SilentTristero]

Sorry, try this: http://phys.org/news/2015-11-n...

Re:In MWI, this is obvious

[lucien86]

A much simpler explanation is that general relativity fails at the light speed barrier. In that case we only need three dimensions and one universe. General relativity still works except that the time dimension is restricted to quantum scales..

Misleading title

[burtosis]

Unless nasa has gotten some really interesting data from SETI im pretty sure its from outside of the light cone of the experiment, not an actual event horizon of the black hole.

Not that the actual paper or press release is linked at this time (who reads those?) but there have been experiments lately that close loopholes in bells theorm and show that the details are truly random until measured yet correlated upon measurement. This includes determining the experiment details randomly from outside the light cone of the experiment using advances in optical measurement of single photons and random number generation.
link to a related article

Re:Misleading title

[Anonymous Coward]

What does SETI have to do with NASA beyond some initial resources and partial funding 40 odd years ago?

SETI is a waste of time, money and energy. It's utterly ridiculous, no better than muslim's thinking their jesus character is almost upon us.

Information is lost

[mbone]

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.

Re:Information is lost

[burtosis]

If you read the paper information is not lost

Conclusions
In conclusion, thermal Hawking radiation stimulated by quantum vacuum fluctuations has been observed in a quantum simulator of a black hole. This confirms the prediction of Hawking regarding spontaneous pair production in the presence of a horizon. This has implications beyond the physics of black holes, as it confirms the semiclassical step toward the understanding of quantum gravity. The Hawking spectrum is observed, as are the correlations between the Hawking radiation exiting the black hole and the partner particles inside the black hole. These correlations are surprisingly narrow in position space, which implies that the high frequency tail of the distribution of Hawking pairs are entangled. On the other hand, the overall weakness of the correlations in position space implies that the low frequencies are not entangled. The entanglement confirms that there is an issue of information loss within the semiclassical approximation.

Re:Information is lost

[mbone]

I don't follow that - I interpret "issue of information loss" as meaning that it is happening - i.e., that there is loss to worry about. Read at the bottom of page 1

Furthermore, the entanglement implies that the outgoing Hawking particles cannot be entangled with one another at various times. This shows
that there is indeed an issue of information loss in a black hole, within the semiclassical approximation

Entanglement survives across the event horizon (at least, in this analogue). It would be presumably destroyed at the singularity. There is (at least, in this analogue) no black hole firewall, no entanglement with previously emitted particles, no wormholes or other such exotica.

As for the frequency dependence, I will wait on that. That may be profound, or it may be an experimental error or some restriction imposed by the black hole analog setup. We should know soon enough.

Re:Information is lost

[burtosis]

Yes it's an interesting result that should point the way for more definitive study. The notion of the singularity is not well defined and may be more of a layered structure than a boundary that applies to all particles at all times ever to fall in. It would be interesting in an actual test case as the sonic approximation model suggests entanglement is preserved for higher frequencies but does rely on many (interesting) assumptions.

Re:Information is lost

[mbone]

Yes, who would have thought that a black hole could have multiple singularities (and even maybe, just maybe, life) inside it.

Re:Cern isn't even right about the higgs's boson

[Ramze]

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.

Re: Dumb Holes?

[Anonymous Coward]

Once I saw that your first post was written by an idiot, I immediately knew that your second post was written by an idot as well. Its logic, dumbass.

Re:Dumb Holes?

[reboot246]

A billionaire businessman and a successful brain surgeon have nothing on you, right?

Get back to me when you match their success.

Re:Dumb Holes?

[h33t l4x0r]

Well, I'm pretty sure I know what the pyramids were for. Also 0% ob the people I've stabbed with murderous intent have survived so I'm winning there as well :)

Re: Dumb Holes?

[h33t l4x0r]

Quantum entanglement requires a pair, AC. But thanks for playing!

But what about

[Anonymous Coward]

Imperial Entanglements? Can we at least avoid those

Re:Dumb Holes?

[Anonymous Coward]

Why would he want to get back to *you* after achieving such success? I would assume he would discount your priceless advice even more. Even more disturbing is the fact that you advertise the fact that your opinion is so easily swayed by money. The truth is, we just can't have a president going around stabbing people. It's just not acceptable outside of the middle east. I guess Hillary and the terrorists have won.

Re:Dumb Holes?

[Anonymous Coward]

I personally find smart holes more satisfying. And cookies, don't forget the cookies.

No such thing

[Roger W Moore]

So tachyons or neutrinos are "below quantum"? If so, what does it mean to be below quantum?

There is no such thing as "below quantum". Tachyons don't exist (or at least we have zero experimental evidence that they do) and neutrinos are most decidedly quantum in nature since they are extremely well described by quantum field theory.

Some corrections

[Roger W Moore]

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.

Re:Dumb Holes?

[Anonymous Coward]

Are you willing to give him a billion dollars to get started with?

Oh, wait, you aren't? So, how about you give him a cup of shut the hell up.

Cherenkov radiation

[Roger W Moore]

neutrinos merely go faster than light when that light goes through a non-vacuum medium, like beta radiation that makes a nuclear reactor glow blue in the swimming pool.

The blue glow is Cherenkov radiation which is caused by electrons from beta decay of fission products travelling through the water faster than the speed of light in water. However only charged particles cause Cherenkov light and neutrinos, being neutral, will not cause this effect and pass through matter almost entirely unaffected unless they have extremely high energies and even then they interact via the weak force and not electromagnetism.

Re: Dumb Holes?

[Impy the Impiuos Imp]

So Hillary and Bernie are quantum entagled AND faced with imminent Pauli Exclusion Principle issues!

Feel better now?

Hawking is wrong

[Anonymous Coward]

So there is no such thing as a black hole information paradox, and no reason to create nonsense such as hawking radiation after all? Interesting.

Re:Dumb Holes?

[ChrisMaple]

Either you are admitting to murder or you don't know that 0 divided by 0 is undefined in most reasonable contexts.

ELI5, please help me understand

[wwalker]

So, one thing I don't understand about quantum entanglement. In the simplest terms, you can have 2 photons generated from a specific process, and if you measure the spin (polarization?) of one of the photons, the other one will always have the opposite spin. And that's what they call quantum entanglement, right? But to me it simply means that the said specific process always generates a pair of photons with opposite spin. Where is the magic of entanglement here? Please help me understand. It's kind of like if we take an apple and slice it in two, and then measure one of the halves, the other will always be facing the other way. Well, yeah, we just sliced an apple in two halves, so no surprise there, they'll always be facing each other. What am I missing?

Re:ELI5, please help me understand

[Anonymous Coward]

The magic is that the paired spins are not predetermined, and cannot be known (Bell's theorem) until one is measured, at which time the other one is known to collapse to the other state. To put in the context of an apple, pretend we know that one half has a worm. Until measurement, the wavefunction describing both halves has a worm in each half!. Cutting the apple (measurement) forces the wavefunction to collapse and the worm to now reside in one piece.

Re:ELI5, please help me understand

[Anonymous Coward]

Because there are operations you can perform on the photons and they don't behave like each one is up and down. A comment above gives one example using spin, and there are many more written about online already and in more detail/clarity. Look for an explanation of Bell's inequality at an appropriate level for your interests.

Re:ELI5, please help me understand

[Bite The Pillow]

I can't explain it like you're five, because you're not five and you have been indoctrinated into the classical world. But this video is pretty good.

https://www.youtube.com/watch?...
"Quantum Entanglement & Spooky Action at a Distance "

If you haven't grasped the quantum way of thinking, this next one is a great video. It doesn't get all technical and assumes some basic information, but the pictures should start you in the quantum direction.

https://www.youtube.com/watch?...
"Delayed Choice Quantum Eraser Experiment Explained"

I have what appears to be an apple, and you have what appears to be an identical apple. When I slice mine in half, half of my apple disappears, and half of your apple disappears. But not just any half - the way I cut my apple determines which half you get. If there is a bruise, it will be either on my half or on your half. Putting the halves together gives us exactly the apple that we appeared to have before it was sliced.

In quantum terms, it is much as the video above describes the double slit experiment - the photon or electron goes through both slits, so it is in 2 places at once. That is how we both appear to have the same apple in the beginning. Slice the apple, same as measuring the photon, and it collapses into the two halves.

We can create photons that are not entangled, and they do not behave the same way. What happens at detector 0 in the second video is inexplicable, currently, but that's entanglement.

Re:ELI5, please help me understand

[Anonymous Coward]

No, that's amore.

As somebody who worked on entanglement

[drolli]

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.

Gentle measurement preserves superposition.

[Anonymous Coward]

What about techniques that can extract information without destroying the superposition? You could take two pairs of entangled particles, and observe one (destroying superposition) and either observe or not observe the other one. The remote end peeks at the pair, and if one is no longer in a superposition takes the state of the other (superposition or collapsed) as a bit of information. See: http://m.phys.org/news/2012-10-gently-cubit-superposition.html

Re:Gentle measurement preserves superposition.

[drolli]

You are talking about non-demolition measurements, but these are a different issue, since they do actually not leave the state undisturbed, but only do a "pure measurement" i.e. project its own state precisely into one of the conjugate variables of the quantum system, and leave the other one intact.

since entanglement is....

[modmans2ndcoming]

since entanglement is the like writing a 1 on one index card and writing a 0 on another, then dropping the envelopes into a box, grabbing one of the envelopes and opening it which reveals what the value of the card in the box is, I would expect this situation to be the case.

Re:Dumb Holes?

[fahrbot-bot]

A billionaire businessman and a successful brain surgeon have nothing on you, right?
Get back to me when you match their success.

One has been divorced two more times than me than me and declared bankruptcy four more times and may or may not have more hair than me. The other can apparently sleep while standing, sitting and conversing and may or may not have tried to stab his friend (or relative) while trying to decide whether to accept his "scholarship" to West Point, before reminding a robber to rob someone else.

All in all, I think I'm doing pretty well - in comparison. Occupation, money and success aren't everything.

Re:Ethan is a dickhead.

[HiThere]

I disagree. It would probably have lasted at least 6 months.

Re: Dumb Holes?

[Anonymous Coward]

Two posts don't make a pair? Who knew?

WHAT is "successful" about Trump?

[Anonymous Coward]

He would be billions ahead if he'd taken the money he had 30 years ago and just stuck it in an Index Tracker fund.

He's shut down through his incompetence scores of businesses, more even than Shrub.

So what is "successful" about Trump? Other than successfully popping out of Mrs Trump's billionaire cloaca? With a headstart like that ANY moron could manage to get billions.

WRONG!!!!

[Anonymous Coward]

it depends on how you get to 0.

x/x=1 no matter what value x is, even if it's zero.

0/x=0 no matter what value x is, even if it's zero.

And in Riemann (and complex) number systems, 1/0=infinity, and makes entirely fine sense. It's only in counting where depending on your end clause, you either get 0, 1 or infinity, and that's not really "undefined", but "depends on what you start your definition as".

0 will go into 0 infinite times if you count until you have fewer than your (zero) step left.
0 will go into 0 once if you count how many you can loop round
0 will go into 0 zero times if you count the remainder and stop when you get to zero, and increase your count if there's any left.

This doesn't mean it's undefined.

And it IS defined, depending on how you get your zeros.

See the zero rest mass of the photon when it goes to light speed (therefore multiplied by 1/0). It's not zero any more. It's a very defined value.

Re:WRONG!!!!

[sexconker]

You're an absolute idiot.

Division by 0 is undefined.

Re:WRONG!!!!

[Anonymous Coward]

NAILED your ignorant a$$

Re:WRONG!!!!

[lucien86]

Its undefined unless you define it.
- Division by zero does have a defined value of - imaginary infinite. That is a positive infinity and a negative infinity, or if you sum them together zero.
- An alternative derived using permutation also sums to zero, with the numerator becoming the remainder.. This is the value that computer ALU's would actually produce if allowed to calculate division by zero..

0/0 = 1 is just a formalism, and is technically incorrect because it produces a signed value from a signless operation.. A similar formalism is to assign the value of roots as positive when in reality their sign is by definition unknown. m^2 = n, root (n) = +m or -m.

Re:WRONG!!!!

[sexconker]

0/0 does not equal 1, and anyone ever stating that it does needs to be shot in the fucking face.

Division by zero is undefined. It is not infinite - positive or negative. It is incalculable by the definition of the operation of division.

It is not a "formalism" to state anything other than the fact that it is undefined. It is not a formalism to state roots as positive values, either. Maybe I'm old, but I ALWAYS consider both positive and negative values unless I explicitly limit my domain. To do otherwise would be flat out fucking wrong.

Re:WRONG!!!!

[lucien86]

You can dry run a computer division by zero operation, and the operation produces a result of zero leaving a remainder that equals the nominator. At its heart division is a multiple subtraction and the result is an accumulation therefore division by zero produces zero..
On the opposite when you do the formal theory of calculus you get to play with infinitesimals and zero, and the infinitesimals map the graph of division and multiplication by zero - to produce the familiar tangent curve. (summing the (+)(-) infinity to zero is my own observation) Quite a lot of complex maths in there, Riemann spheres, Riemann metric, inner products, etc.. https://en.wikipedia.org/wiki/... Cant say that I understand half of it myself, but its the maths that leads to tensor manifolds, Lie algebras, and General Relativity..

Re:WRONG!!!!

[Anonymous Coward]

At its heart division is a multiple subtraction and the result is an accumulation therefore division by zero produces zero..

Holy crap. Go back to high school.

Ken Spam

[AndyKron]

How do they know it survives through the event horizon, were they there? -Ken Spam

Re:Dumb Holes?

[sexconker]

Percent means "per hundred". Percentages are calculated by dividing by 100. 0/100 = 0.
I have no idea why you're trying to talk about 0/0, which is undefined.

Wow! I missed the launch of that mission

[Anonymous Coward]

When did we launch that probe into the black hole? You know, the probe that contained the half of a quantum-entangled pair whose other half we held far away from the back hole. What was the mission called? (I just cannot seem to recall)

Oh, [yawn] it's just another daydream re-named as a "thought experiment" and slathered with conjecture about a few things we think we might understand based on a few things we think we saw in a telescope.

I get it: there are people who are endlessly fascinated about postulations about things in distant galaxies, but we have never been to those places, never sent probes there, etc. It's all just theories based on very poor and very sparse remote observations, sprinkled with a liberal dose of assumptions that our beliefs about conditions there are close enough to conditions here that we even CAN make valid conclusions from what we think we are seeing. Put this in the category of "comic book science" and consider it for use as technobabble to fill-in plot holes in the new Start Trek series. This does not belong in the same category as actual science. Conjecture about things like quantum entanglement around black holes belongs in a place far less authoritative than conjecture about the core of Jupiter, which itself does not belong in the same books with actual data about the top layer of clouds of Jupiter or the actual data about the moons of Jupiter. People need to learn to discriminate between actual pictures and "concept art", between hard data and suppositions. I grow weary of people who worship at the altar of people who've built entire careers pretending that their random imaginings are equivalent to science - this stuff is just an alternate religion when it's this thin on actual data.

faster than light

[slashmydots]

"and then the other — even if it's across the Universe — is immediately known"
Well I guess that's settled then. A year or two ago I posted that scientists potentially thought that quantum changes could occur faster than light because nothing is "traveling" it's merely updating to current reality in real time. People replied like crazy and downvoted me to oblivion. Well I guess we found out who was right after all, didn't we? In fact I recall a story about NASA wanting to test this onboard the ISS. I think that rocket carrying it exploded but still.

Quantum encryption protocol BB-84

[SharpFang]

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!"

Re:Quantum encryption protocol BB-84

[Anonymous Coward]

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.

This isn't true. Two photons with entangled polarity are guaranteed to have a polarization somehow related to each other (the same, opposite, etc) but do not interact further. It's like saying "smash these two things together and they will fracture in this way so you can relate the fragments together in this way" and that's it. They "share" a state that is relative only because of the initial conditions, subsequent changes don't imply a change. When a wavefunction "collapses" it just means they are no longer related. The whole concept is over-hyped, it makes for a fancy way of sharing crypto keys that would be very difficult to apply a man-in-the-middle attack to but aside from the complexity of doing so is no better than less-sophisticated methods (like an LC circuit where each party has their own variable resistor.)

Re:Quantum encryption protocol BB-84

[SharpFang]

Do they need to interact further?

They collapse when one passes through one polarizer. This will result in the other, passing through the other polarizer in a "modulo 90" orientation to behave predictably, either pass at mathing polarity or vanish at wrong polarity, with no uncertainty; "the same" measurement gets repeated, producing "the same" results.

If one passes at a "superfluous" polarizer at 45 degrees orientation, their wavefunction collapses to that. Afterwards, being no longer entangled, they may pass two "matching orientation" polarizers and produce different results. That's all that's needed to confirm the wavefunction has collapsed.

Yes, that's not all that much, yes it's a way to share keys in a taper-evident way, and yes there's a hype with misunderstanding the consequence of simultaneous collapse of wavefunction, coming from belief that the fact of the collapse is somehow recognizable without standard communication between the two ends. That's the purpose of my post: to show that it can be useful but it doesn't allow faster-than-light communication because the "information" that did travel faster than light is undistinguishable from random noise without a-posteriori standard communication.

Would you mind explaining the LC concept? It sounds quite interesting.

Alternative representation

[Anonymous Coward]

How about matter is positive, antimatter is negative, and stuff that can't be represented physically is a complex number?

Re:Alternative representation

[lucien86]

Oh boy if only it were that simple. Technically the modern definition of antimatter defines it as matter with positive mass but opposite charge. We can add another type of antimatter that has negative mass, but this isn't generally compatible with a lot of modern physics theory, which says that with negative mass you also get negative time. I'm working on a new physics model that solves this problem, but to do it the model has to replace general relativity at FTL speeds with a new modified 'absolute frame' model.. There's a reason that Einstein hated the FTL , its maths is complex disjointed and not pretty..

If true...

[Anonymous Coward]

Could you not simply throw an entangled particle into a black hole and use it to measure what's inside? Not sure what useful (if any) information you would be able to get, but couldn't this allow information to be retrieved from inside the even horizon (something which I believe is considered currently impossible)?

Re:Dumb Holes?

[doccus]

I've known a few. Whenever they are around, everything intelligent seems to get sucked away.

Hey be nice! I was ENGAGED to one!

Re:Dumb Holes?

[Anonymous Coward]

Percent means "per hundred". Percentages are calculated by dividing by 100. 0/100 = 0.
I have no idea why you're trying to talk about 0/0, which is undefined.

Nowhere does he say "percent".. or even imply it. Furthermore he gives a proper explanation of all the terms and I clearly recall the same formulae used in school .. although admittedly it was 50 years ago so my memory might be a touch hazy. Never the less I would choose a well explained response such as his over your strawman response (he never mentions percent at all) or the other "you're an absolute idiot" reply which imparts little in the way of defense of an argument !

Re:Dumb Holes?

[beastofburdon]

Please don't remind me of the supply officer on that damn submarine!

Re:Dumb Holes?

[david_thornley]

Undefined, for 0/0, means that any value is permissible. For different uses, it can mean no value is permissible. In this case, 0% is a perfectly valid answer, since 0*0 = 0. Any other answer is possible; for example, 53.6% of the people I've stabbed with murderous intent survived.

LOL, look everyone: It's lucien... apk

[Anonymous Coward]

See subject: The libelous little "SiDeWaLk-ShRiNk" w/ delusions of grandeur of being a psychiatric pro -> http://slashdot.org/comments.p...

* Truth be told he's just a little punk that needs to get his jaw busted...

APK

P.S.=> Is that WHY "your kind" sits around forums *trying* to "play smart" under fake names, trolling like the little bitch weasel you evidenced yourself to be in the link above, & yet from perusing your history here just now, you tend to stay in areas only dealing in totally ambiguous shit most of the time, like "things political" over which you have no control either & aren't a mover in them? Trying to be "the smartest person in the room" eh?? I shut your dimwitted libelous little ass down easily, punk... apk

Re:Dumb Holes?

[RockDoctor]

A billionaire businessman who is an absolute arsehole (we've got Trump developments in our area ; we know what he's really like, not what his PR people paint him as) and a brain surgeon who is a fucking idiot in addition to being a religious dimwit?

Yeah, I'm better than the both of them put together.