5 ms·

i fail to see whats mysterious about knowing something without direct proof. You could put a literal orange cube in a box, ship it across the galaxy, and you'd

i fail to see whats mysterious about knowing something without direct proof. You could put a literal orange cube in a box, ship it across the galaxy, and you'd "know" anyone opening the box would be an orange cube. You don't need to be present at the unboxing to know that with certainty. How is this different? Am I missing something?

im3w1l 9y ago
Allow me to give a more (but not perfectly) accurate analogy. I give you a magic piece of paper with a two binary digits (00/01/10/11) on it. I also keep such a paper for myself. If we both start by looking at our first digits then those will mysteriosly match, but if we then look at our second digits they will have just a 50% chance of matching. However, if we both start by looking at the last digits, then those will match, and our first digits will have a 50% chance of matching. If you and I start by looking at different digits, then the digits we read are just standard random bits. The cool thing about this is that our magic paper will also work instantly even if we are lightyears apart. However, if you decide to look at the last digit and you see a 1, then that tells you nothing about me or which digits (if any) I have looked at, so I can't send you a message with this paper.
- kbenson 9y ago
  It sounds like an interesting, if very expensive, way to get around primes for key exchange, in the world where prime factorization is much more efficient. Need a random number, look a bun of shared digits in a predefined order. You now have a shared random number that's perfectly secure, as long as you shipped out your shared state in advance.
coldtea 9y ago
That this example has very little to do with entanglement, which is not merely "knowing without direct proof". We do that everyday. The same way, the issue with Shroedigger's cat is not that "the cat is in a single state, but we just don't know whether that's dead or alive unless we open the box" (as many laymen try to explain it). That's just "I don't know yet" and has nothing to do with the issue Shroedigger tried to highlight or quantum mechanics (not to mention that this we encounter everyday and we can replicate perfectly with say, a box and a person that throws a dice and based on that releases or not a gas in the box with a cat -- that's not what the paradox is about). For entanglement, see this: https://www.sciencealert.com/watch-this-is-how-quantum-entanglement-really-works https://www.sciencealert.com/watch-this-is-how-quantum-entan...
IanCal 9y ago
If I understand right, this starts to touch on Bell's Theorem. The description as is means that the situation is identical if there's "spooky action at a distance" or if there's none and you just don't know what's in each box until you open one (and therefore can guarantee what's in the other). There are predictions from this however that when tested just don't work. There is something else going on. I would go further but I'm sure my explanations would contain huge inaccuracies that probably would cause more problems with understanding what's happening so will link you to a couple of things: https://en.wikipedia.org/wiki/Bell%27s_theorem https://en.wikipedia.org/wiki/Bell%27s_theorem http://www.askamathematician.com/2010/06/q-how-it-is-that-bells-theorem-proves-that-there-are-no-hidden-variables-in-quantum-mechanics-how-do-we-know-that-god-really-does-play-dice-with-the-universe/ http://www.askamathematician.com/2010/06/q-how-it-is-that-be... I'm sure there are others here who are well versed in this who can chip in.
lucozade 9y ago
With quantum entanglement, what happens to one particle prior to measurement affects the other even if the effect occurred after they were parted. That's where it gets really spooky. To belabour the colours and boxes analogy: We have 2 balls, if one is orange the other is always purple and vice versa. Now these balls have an extra property. If you shake them vigorously they may or may not change colour randomly. So, we put them in boxes without looking and take them far away from each other. Now, some time after they are far apart and before you look in the box, you shake one of the boxes. You then look. In QM, if the ball you observe is orange(purple) then you know the other is purple(orange). But the other ball can't have known ahead of time that a) you were going to shake your one and b) that it changed colour (or didn't). That's why it's spooky.
- novalis78 9y ago
  Sounds like they never were two separate entities to begin with or never parted location. Which is spooky too, in a different way.
  - berdon 9y ago
    Too build on this thought - is it possible that these quantum properties aren't affected by locality? Which is obviously true given the explanation above... I guess I'm asking if there are other intuitions that can be made if locality is explicitly considered unrelated.
  - lucozade 9y ago
    When I first started to be interested in this area, it occurred to me that it might be something like a 'stretchy' spacetime i.e. the particles are actually locally connected but appear unconnected if you use a static spacetime as a reference as we tend to. I guess something analogous to the idea that someone moving close to c experiences time different from someone in a slow moving reference frame. Unfortunately, I have neither the experience nor ability to progress that thought much further so, if someone wants to go off and get a Nobel from it, feel free...
  - felipemnoa 9y ago

im3w1l 9y ago

Allow me to give a more (but not perfectly) accurate analogy. I give you a magic piece of paper with a two binary digits (00/01/10/11) on it. I also keep such a paper for myself. If we both start by looking at our first digits then those will mysteriosly match, but if we then look at our second digits they will have just a 50% chance of matching. However, if we both start by looking at the last digits, then those will match, and our first digits will have a 50% chance of matching. If you and I start by looking at different digits, then the digits we read are just standard random bits. The cool thing about this is that our magic paper will also work instantly even if we are lightyears apart. However, if you decide to look at the last digit and you see a 1, then that tells you nothing about me or which digits (if any) I have looked at, so I can't send you a message with this paper.

kbenson 9y ago
It sounds like an interesting, if very expensive, way to get around primes for key exchange, in the world where prime factorization is much more efficient. Need a random number, look a bun of shared digits in a predefined order. You now have a shared random number that's perfectly secure, as long as you shipped out your shared state in advance.

coldtea 9y ago

That this example has very little to do with entanglement, which is not merely "knowing without direct proof". We do that everyday. The same way, the issue with Shroedigger's cat is not that "the cat is in a single state, but we just don't know whether that's dead or alive unless we open the box" (as many laymen try to explain it). That's just "I don't know yet" and has nothing to do with the issue Shroedigger tried to highlight or quantum mechanics (not to mention that this we encounter everyday and we can replicate perfectly with say, a box and a person that throws a dice and based on that releases or not a gas in the box with a cat -- that's not what the paradox is about). For entanglement, see this: https://www.sciencealert.com/watch-this-is-how-quantum-entanglement-really-works https://www.sciencealert.com/watch-this-is-how-quantum-entan...

IanCal 9y ago

If I understand right, this starts to touch on Bell's Theorem. The description as is means that the situation is identical if there's "spooky action at a distance" or if there's none and you just don't know what's in each box until you open one (and therefore can guarantee what's in the other). There are predictions from this however that when tested just don't work. There is something else going on. I would go further but I'm sure my explanations would contain huge inaccuracies that probably would cause more problems with understanding what's happening so will link you to a couple of things: https://en.wikipedia.org/wiki/Bell%27s_theorem https://en.wikipedia.org/wiki/Bell%27s_theorem http://www.askamathematician.com/2010/06/q-how-it-is-that-bells-theorem-proves-that-there-are-no-hidden-variables-in-quantum-mechanics-how-do-we-know-that-god-really-does-play-dice-with-the-universe/ http://www.askamathematician.com/2010/06/q-how-it-is-that-be... I'm sure there are others here who are well versed in this who can chip in.

lucozade 9y ago

With quantum entanglement, what happens to one particle prior to measurement affects the other even if the effect occurred after they were parted. That's where it gets really spooky. To belabour the colours and boxes analogy: We have 2 balls, if one is orange the other is always purple and vice versa. Now these balls have an extra property. If you shake them vigorously they may or may not change colour randomly. So, we put them in boxes without looking and take them far away from each other. Now, some time after they are far apart and before you look in the box, you shake one of the boxes. You then look. In QM, if the ball you observe is orange(purple) then you know the other is purple(orange). But the other ball can't have known ahead of time that a) you were going to shake your one and b) that it changed colour (or didn't). That's why it's spooky.

novalis78 9y ago
Sounds like they never were two separate entities to begin with or never parted location. Which is spooky too, in a different way.
- berdon 9y ago
  Too build on this thought - is it possible that these quantum properties aren't affected by locality? Which is obviously true given the explanation above... I guess I'm asking if there are other intuitions that can be made if locality is explicitly considered unrelated.
- lucozade 9y ago
  When I first started to be interested in this area, it occurred to me that it might be something like a 'stretchy' spacetime i.e. the particles are actually locally connected but appear unconnected if you use a static spacetime as a reference as we tend to. I guess something analogous to the idea that someone moving close to c experiences time different from someone in a slow moving reference frame. Unfortunately, I have neither the experience nor ability to progress that thought much further so, if someone wants to go off and get a Nobel from it, feel free...
- felipemnoa 9y ago