Quantum Entanglement & Spooky Action at a Distance

Quantum Entanglement & Spooky Action at a Distance


– In the 1930s, Albert Einstein was upset
with quantum mechanics. He proposed a thought experiment where, according to the theory,
an event at one point in the universe could instantaneously affect another event arbitrarily
far away. He called this “spooky action at a distance” because he thought it was absurd.
It seemed to imply faster than light communication, something his theory of relativity ruled out.
But nowadays, we can do this experiment, and what we find is, indeed, spooky. But in order
to understand it, we must first understand spin. All fundamental particles have a property
called spin. No, they’re not actually spinning, but the analogy is appropriate. They have
angular momentum, and they have an orientation in space. Now, we can measure the spin of
a particle, but we have to choose the direction in which to measure it, and this measurement
can have only one of two outcomes. Either the particle’s spin is aligned with the
direction of measurement, which we’ll call spin up, or, it is opposite the measurement,
which we’ll call spin down. Now, what happens if the particle spin is vertical, but we measure
it’s spin horizontally? Well then, it has a 50% chance of being spin up, and a 50% chance
of being spin down, and after the measurement, the particle maintains this spin, so measuring
its spin actually changes the spin of the particle. What if we measure spin at an angle
60 degrees from the vertical? Well now, since the spin of the particle is more aligned to
this measurement, it will be spin up 3/4 of the time, and spin down 1/4 of the time. The
probability depends on the square of the cosine of half the angle. Now, an experiment like
the one Einstein proposed can be performed using two of these particles, but they must
be prepared in a particular way. For example, formed spontaneously out of energy. Now, since
the total angular momentum of the universe must stay constant, you know that if one particle
is measured to have spin up, the other, measured in the same direction, must have spin down.
I should point out, it’s only if the two particles are measured in the same direction that their
spins must be opposite. Now here’s where things start to get a little weird. You might imagine
that each particle is created with a definite well-defined spin, but that won’t work, and
here’s why. Imagine their spins were vertical and opposite. Now, if they’re both measured
in a horizontal direction, each one has a 50/50 chance of being spin up. So, there’s
actually a 50% chance that both measurements will yield the same spin outcome, and this
would violate the law of conservation of angular momentum. According to quantum mechanics,
these particles don’t have a well-defined spin at all. They are entangled, which means
their spin is simply opposite that of the other particle. So, when one particle is measured,
and its spin determined, you immediately know what the same measurement of the other particle
will be. This has been rigorously and repeatedly tested experimentally. It doesn’t matter at
which angle the detectors are set, or how far apart they are, they always measure opposite
spins. Now just stop for a minute, and think about how crazy this is. Both particles have
undefined spins, and then you measure one, and immediately you know the spin of the other
particle, which could be light-years away. It’s as though the choice of the first measurement
has influenced the result of the second faster than the speed of light, which is, indeed,
how some theorists interpret the result. But not Einstein. Einstein was really bothered
by this. He preferred an alternate explanation, that all along the particles contained hidden
information about which spin they would have if measured in any direction. It’s just that
we didn’t know this information until we measured them. Now, since that information was within
the particles from the moment they formed at the same point in space, no signal would
ever have to travel between the two particles faster than light. Now, for a time, scientists
accepted this view that there were just some things about the particles we couldn’t know
before we measured them. But then along came John Bell with a way to test this idea. This
experiment can determine whether the particles contain hidden information all along, or not,
and this is how it works. There are two spin detectors, each capable of measuring spin
in one of three directions. These measurement directions will be selected randomly, and
independent of each other. Now, pairs of entangled particles will be sent to the two detectors,
and we record whether the measured spins are the same, both up, or both down, or different.
We’ll repeat this procedure over and over, randomly varying those measurement directions,
to find the percentage of the time the two detectors give different results, and this
is the key, because that percentage depends on whether the particles contain hidden information
all along, or if they don’t. Now, to see why this is the case, let’s calculate the expected
frequency of different readings if the particles do contain hidden information. Now, you can
think of this hidden information like a secret plan the particles agree to, and the only
criterion that plan must satisfy is that if the particles are ever measured in the same
direction, they must give opposite spins. So, for example, one plan could be that one
particle will give spin up for every measurement direction, and its pair would give spin down
for every measurement direction. Or another plan, plan two, could be that one particle
could give spin up for the first direction, spin down for the second direction, and spin
up for the third direction, whereas its partner would give spin down for the first direction,
spin up for the second direction, and spin down for the third direction. All other plans
are mathematically equivalent, so we can work out the expected frequency of different results
using these two plans. Here, I’m visually representing the particles by their plans,
their hidden information. With plan one, the results will obviously be different 100% of
the time. It doesn’t matter which measurement directions are selected, but it does for particles
using the second plan. For example, if both detectors measure in the first direction,
particle A gives spin up, while particle B gives spin down. The results are different.
But if instead, detector B measured in the second direction, the result would be spin
up, so the spins are the same. We can continue doing this for all the possible measurement
combinations, and what we find, is the results are different five out of nine times. So,
using the second plan, the results should be different 5/9 of the time, and using the
first plan, the results should be different 100% of the time, so overall, if the particles
contain hidden information, you should see different results more than 5/9 of the time.
So what do we actually see in experiment? Well, the results are different only 50% of
the time. It doesn’t work, so the experiment rules out the idea that all along, these particles
contain hidden information about which spin they will give in the different directions.
So, how does quantum mechanics account for this result? Well, let’s imagine detector
A measures spin in the first direction, and the result is spin up. Now, immediately you
know that the other particle is spin down if measured in the first direction, which
would happen randomly 1/3 of the time. However, if particle B is measured in one of the other
two directions, it makes an angle of 60 degrees with these measurement directions, and recall,
from the beginning of this video, the resulting measurement should be spin up 3/4 of the time.
Since these measurement directions will be randomly selected 2/3 of the time, particle
B will give spin up 2/3 times 3/4 equals half of the time. So both detectors should give
the same results half of the time, and different results half of the time, which is exactly
what we see in the experiment. So quantum mechanics works. But there is debate over
how to interpret these results. Some physicists see them as evidence that there is no hidden
information in quantum particles, and it only makes sense to talk about spins once they’ve
been measured, whereas other physicists believe that entangled particles can signal each other
faster than light to update their hidden information when one is measured. So, does this mean that
we can use entangled particles to communicate faster than light? Well, everyone agrees that
we can’t. And that is because the results that you find at either detector are random.
It doesn’t matter which measurement direction you select, or what’s happening at the other
detector, there’s a 50/50 probability of obtaining spin up or spin down. Only if these observers
later met up and compared notebooks, would they realize that when they selected the same
direction, they always got opposite spins. Both sets of data would be random, just the
opposite random from the other observer. That is, indeed, spooky, but it doesn’t allow for
the communication, the sending of information from one point to another, faster than light,
so it doesn’t violate the theory of relativity. And that, at the very least, would make Einstein
happy.

100 thoughts on “Quantum Entanglement & Spooky Action at a Distance

  1. I assume this video is super smart and is explaining things really well and was well thought out… because I have zero of those things after watching this. In fact, I think I may be dumber. While I don't want to fault the creator… is there really not a better way to explain this? That was confusing as heck to me.

  2. Had to watch the last 3/4th video twice to understand it whole becuase I only got the half of it.

  3. Is the entanglement properties the same as perhaps the opposite corner of a square? If we move one dot of the corner, then the opposite corner will also move, even though its not dirrectly touching it. The same as entanglement, perhaps there are dimension beyond our 3D that entangled them, so as we measute its properties, the other's is determined? Im just speaking nonsense. Please correct me

  4. The particles contain secret information that I still am not privy to… %100 of the time no matter in what direction they are being measured in spin up or spin down. #sheeeeesh

  5. There are a number of incorrect assumptions made in this video and regarding this theory.
    first though how is the experiment tested the video claims it is possible but I find no mention of how or where it has been done.
    Incorrect assumptions-

    1. The way the conservation of angular momentum is applied to the universe.
    If this is a theoretical experiment only then our experiment breaks one or more natural laws to start off, specifically the creation of mass, and so of course there will be other incompatibilities with natural laws to balance this out. The equation
    Angular Momentum = Mass * Angular Velocity
    is used as a definition and means to determine angular momentum. It should be clear that if you keep mass and angular velocity the same then the momentum should stay the same. However when we change the mass the angular velocity will change as well. We can apply this logic to the "system of the universe" as well
    Angular Momentum of Universe = the sum of (all the masses in the universe * their respective angular velocities)
    If from one moment to the next the any mass is added or removed the total of the angular momentum of the Universe need not remain constant. To summarize if we create a pair of masses from nothing it doesn't have to sum to no net angular momentum.
    This can be bypassed by having a mass with no angular momentum relative our reference point and dividing it into 2 equal mass parts with some angular momentum. According to the law of conservation of angular momentum the 2 parts would have equal magnitude and opposite sign/direction angular momentum. Assuming the direction is unknown and random we can proceed with the thought experiment.

    2. an inaccurate measurement (the spin measurement of a particle's spin when the spin is actually perpendicular to the direction of measurement) does not change the spin of the particle as is claimed in this video. This would only be possible if the measurement process or device changed the direction, which invalidates the process because a change to one particle does not affect another non connected particle even if it previously was identical in all ways except spin direction.

    3. causation is being attributed to the second particle's spin when it really is correlation. One event caused both the spins rotation.

    4. treating probabilities as absolutes. If the probability of a particle spinning on an axis 60° from the angle of measurement being attributed to the closer axis is 3/4 and the probability of it being attributed to the further axis is 1/4 then the probability of a particle spinning the opposite way on the same axis retaliative to the measurement taken being attributed to the opposite axis of the first particle which we will call Pc can be determined using the following equation
    Pc=Pa²+(1-Pa)²
    where Pa is the probability of the first particle's spin being attributed to the closer axis, and the probability of the second particle's spin being attributed to the axis closest to it's spin would be the same because of the same distance from the measurement. Pa*Pb is the chance both will assign to the closest, (1-Pa)*(1-Pb) is the chance both assign to the further axis. B plugging in the equations above the probability we are looking for is .625. If we want to get the average probability for any angle we would need to integrate this equation (putting back in the sub equation P=cos²(Φ/2)) over the change in angle and account for 3 dimensional space. This would come out something like
    ⌠Φ=180°
    P= │ (2π*cos(Φ)
    *( (cos²(­Φ/2)
    )² + (1-cos²(­Φ/2)
    )² ), Φ)
    ⌡Φ=0°
    I haven't done this sort of math in a long time so I may have messed it up. If you actually care I recommend deriving it yourself.

    5. when testing spin from 3 different angles you assumed because the % result differed from the % expected result based on the probability analysis you rejected the idea of having a singular existing spin. This is a problem because you did not present any statistical significance for the findings. If the test was only done 10 times it would not be unreasonable to get a 50% result. Without providing statistical significance (the probability that the actual results of an infinite number of tests or the entire population would be within some offset range of the sample results, it should look like "from the results the average is 50% with a 95% confidence interval of ±2%) without statistical significance it is wrong to reject the idea.

    6. when calculating the probability of the set of tests presented with 3 angles of measurement and predetermined results for each of the 3 measurements not all the probabilities were given the same weight. there are 8 different sets of predetermined spin possible. The 5/9 number came from the probability of the 2 Up 1 down and its equivalent probabilities, this leaves out the all up and all down possibilities. there are actually 72 equally likely different combinations (8 possible predeterminations multiplied by 9 different orientations of measuring) and 48 result in opposite measurements. This means about 2/3 of the pairs measured should show opposite spin if the theory is to be supported. However if there is any inaccuracy in the measuring devises that can add error, and there will be a random error because this is a sample that error can be reduced with more trials (it increases the confidence in the result and/or narrows the confidence interval)

  6. Does anybody know How two quantum particles entangle? Imagine we have 10 electrons on some phosphorus molecules and use them as Qbits; imagine now that electron A is entangled with electron B but both are not entangled with electron C, which is entangled with electron D. What is the phenomenon that makes a quantum particle to entangle to another and not with a third one?

  7. I feel like there's going to be some combination of this information, combined with traditional cryptographic knowledge that's going to allow us in someway to signal a key for the recipient to know what to expect.

  8. Einstein is not a genius. People still promoting him … well … are not geniuses either. Maybe have a look at some alternative science, that makes a lot more sense. Search YouTube for: Electric Universe

  9. I don't understand the difference/confusion between spin and EM polarization. Can someone explain the correlation or differences? Is one term a simplification of the other? Because I thought Bell was talking about photon polarity…not spin. I thought they were different qualities.

  10. Why are physicists confident that forcing a measurement on entangled particle B have not destroyed its entanglement properties?

    Especially if the experiment was done deliberately so that particle B is not measured in the same orientation as A?

  11. At 2:30 there is a 5 sec explanation about why entangle particles don't have definite spin simply hidden to us. Can someone expand on this? If we accept that entanglement produces particles with opposite spins, why would we ever find them both spin-up??

  12. So if the particle will change it's spin depending on the direction it is observed in, couldn't you observe it in different directions until you get it to spin in the direction you want?
    For example, if you measure vertical and it goes spin up, couldn't you measure again horizontally and get another 50/50 chance of it being spin down?

  13. Q: Do 2 different particles contain information about what direction the other will be from an unforeseen distance?
    A: Experiment Says No.
    Q: What does this have to do with anything?
    A: Instant communication, Instant Download speeds, instant transmission, instant travel basically speed of information will be improved which will improve your life also there are like a trillion other applications for this if it works.

  14. Are we sure that this spin thingy exists?
    It is mentioned with a lot of confidence for something so heavily dependent on probability uncertainty etc.
    What IF the reason people are so perplexed and awed by it is: they don't wanna look stupid, so if there's an equation with symbols that "could mean anything", everyone is afraid to ask what they actually mean and pretends it makes sense.
    I'd like to know:
    Are all "types of subatomic particles" distinguished by their momentum properties relative to the measuring direction?
    What are those other properties?
    How many directions can the momentum based properties be measured from and what are their deviation tolerances until they count as "another" direction? ( what are the angular tolerances that distinguish "up" from "diagonal")
    Regarding the measurements of entanglement for example.
    How do we know, the (admittedly quite impressive) percentage-numbers aren't skewed by those tolerances? (Also if the numbers are always pretty samey- how long until they even out to their respective averages?
    I mean if the measuring direction is important, it is also remarkable, that there's a relatively low number of fundamental particles.
    It IS getting higher and higher though. (not the point but kind of yes)
    I dunno, it quacks like a ponzy scheme, walks like a ponzy scheme…
    I sound douchey in this post but aren't at least the questions legitimate?
    And before you brush me off with a "learn it yourself, it's out there" keep in mind:
    "If you can't explain it simply, you don't understand it well enough"

  15. Hm… But if we make a quantum computer, would we not be able to send messages at these speeds? Also, couldn't this still be important if we did something where, no matter the results, the matter of just determining one side had meaning regardless of distance?

  16. You explained how these spins worked (and lost me several times), but do we know why these things operate the way they do, and could they affect our world in a way we could observe and be aware of.

  17. I thought I was the only one who had trouble following this…after reading the comments….*whew* I feel better

  18. The particle spins and another particle spins and they sometimes have different spins and sometimes they have the same spin….got it lol

  19. Isn't the spin (direction) itself a type of hidden information, that is kind of destroyed when you actually measure it?

  20. It's easier to understand: imagine a matching engraved half heart pendant. You and your SO keep a half heart inside a sealed box. Then you move far from each other, to another country. After a while, you open the box. It has your initial on it. Now guess what initial your SO will find…

  21. Quantum Computing principle. Duality on the subatomic level confirms the attraction and opposition that creates energy,matter, and AI.

  22. Good video, but the exclusive disjunction mentioned at 8:00 ("whereas others") is not an exclusive disjunction, as not containing a hidden variable and communicating faster than the speed of light are not distinct sets. Indeed, according to the findings summarized in this video, only a madman would suggest that there are hidden variables. Further, "…only making sense talking about spins after they are measured" seems completely irrelevant to whether there are or are not hidden variable, as discussing whether or not there is a hidden message in a fortune cookie makes or does not make sense whether there is or is not a hidden message in one or all fortune cookies. Discussion is beside the point in both cases.

    Further the question of making faster-than-light communication possible is a conflation of faster-than-light particle-to-particle communication possible – which is answered in the experiment in the affirmative, with faster-than-light human-to-human communication, which you indicated due to randomness remains impossible. Additionally now, this term "communication" is ill-defined as communication as signalling may or may not contain (usable or any) information. Thus the question is: do the particles update their "hidden information" or do they just communicate their states as locked in oppositional sync. The introduction of the term "information" perhaps implies that the signalling is a conscious signalling as opposed to a signalling that is much more basic. The conflation of the terms communication, signaling and information is best unraveled in study of semiotics. This study requires a different skill set from hard sciences such as physics, thus explaining the confusion at the end of this otherwise well-structured video.

  23. Shouldn't you be able to make a casino since the quantum particles are random. If you get up three times in a row you win. In this way you could play with aliens 1 million lightyears away and get instant results. Or another scenario:

    Robot 1 asks robot 2 on a date. Robot 2 says that it will think about and when she have traveled one million light years in X amount of time robot 1 will take a look at the the quantum particle (sorry I dont know the name when two particles are spooky connected). When robot 2 is at its destination she decided to look at the particle because if its up she will go on the date and if it's down she will not. After she looks what state the particle is in X amount of time has passed and robot two looks at his particle and gets the answer instantly.

  24. 6:15 I though that the entangled photons had to be measured in the same direction in order to give opposite directions.

  25. This was not a very clear explanation of the spooky theory. There are so many better ones. This was totally confusing.

  26. I want to know one thing , have they performed this experiment each at diffrent time…ok i think that the hidden variable is time itself, they planned themself according to time, if u creating the entangled particle at a time they get a plan at the same time to be in up and down spin at let say 12.00 noon and down and up at 12.30 noon so if we measure one of the particle let say at 12.00 noon and other at 12.30 noon if they shows same alignment then definitely time is the hidden variable…i think u get my point…if its something useful then plz plz contact me on my email [email protected],
    Plz i realy want to know if they performed like this or not…..

  27. Looks like we can only exploit things not understand them fully, which makes us more like wizards than scientists.

  28. There is only one type of electrons as showed by cathode tube experiment where all free electrons that emitted from the electron-gun will be deflected to a single spot on a screen behind the cathode tube after interacting with a fixed external magnetic field. If there were two types of electrons (spin up and spin down) then it should have two spots on the screen behind the cathode tube. If you are interested in real discoveries, I would recommend you to read my book, The Unification Theory – Volume One and you will be amazed with lots of new, interesting discoveries. In God I trust.

  29. What am I missing? Why is this not like two (spinning?) balls bouncing off each other, going thier own directions? They have an equal and opposite effect that can be observed light years away. It's not like you can chance the spin of one particle and it changes the other accordingly.

  30. This was a great explanation and visualization of the topic. I'd like to see the data visualized to understand and conceptualize this better.

  31. Is someone going to say something about the fact that 50% of the time the spins were measured as being the same (for the quantum case)…which violates the law of conservation of angular momentum? Am I missing something?

  32. First time I actually completely understood quantum entanglement, thanks🙏
    Although my eyes ache a little with all your spinning 😂

  33. 5 and 9 are components of the ratio used in the conversion calculation between Fahrentheit and Celsius. Now this is beginning to scare me. Coincidence? Perhaps the particles don't have to signal each other; instead they are the same particle in parallel, but diametrically opposed universes.

  34. If both spin directions "UP and Down" for each particle is entangled, we will only be able to use them for transferring information "instantly, with no time" when we find a way to control the spin direction of one of the two entangled spin directions.

  35. Heisenberg's uncertainty principle? If I know position and you measure spin (momentum) at a location, then Heisenberg's equation must be equivalent to 1 x 1 = 1. (Two constants x each other equals a third constant) . If you add two particles its 2(1 x 1)= 2 (1). Add three possible measurements its 3(2(1 x 1) = 3(2(1))). The underlying probability does not change. {If you know momentum and you know position and they are greater than the constant does it imply the constant is wrong for that system?} Are you measuring bells uncertainty or just proving Heisenberg or both?

  36. Lets say my parents bought a pair of slippers and gave one piece (either left foot or right foot) to me and the other piece to my brother in a box, so we dunno what we have. Then my brother travels to Andromeda Galaxy and opens the box. He finds out that he has a left foot slipper, and instantaneously(faster than the speed of light) knows that I have the right foot slipper without contacting me. How is this spooky or amazing? I must be missing something :/

  37. Is there a tilt that favors a spin direction? If so, use it to measure enough entangled particles so that their other halves favor the other direction. Then make lots of money with high frequency trading, provided your entangled pair source can supply you and your partner fast enough.

  38. another example of insanity high up in the academic body. some idiot Bell put together an experiment which didn't show anything and concluded that that that very fact proves that there's no communication .. between particles we know nothing about. he was just playing around, didn't show anything and drew conclusions from it … i could do that, or for that matter, anybody could

  39. The most understandable video I've ever seen about Bell's Inequality. Which is quite a complicated thing. Well Done Derek !

Leave a Reply

Your email address will not be published. Required fields are marked *