4 ms·

I have a question. I just went to a source of physical (quantum) randomness http://www.randomnumbers.info/ http://www.randomnumbers.info/ and I'm giving you a r

I have a question. I just went to a source of physical (quantum) randomness http://www.randomnumbers.info/ http://www.randomnumbers.info/ and I'm giving you a random number between 0 and 10,000 which I've just generated there. Here it goes: 6296. Ok. Now that light cone had finally reached you. And you (neurons in your brain to be precise) are thoughtfully entangled with that random event (outcome), now in your past. Now imagine the following. A few days passes. And you forget that number. A few years passes. Connections between the neurons which were storing this information are now gone. Molecules and atoms which were part of these neurons are gone from your body. There are no entanglements any more which link you to that event. Is that event in your future now? Again?

aaren 12y ago
> There are no entanglements any more which link you to that event. Not directly, but the information has spread out from your neurons into the surrounding matter ad nauseum. It's just we can't interpret the information anymore. The event still happened in your past, you just can't see it through your limited human view of reality.
- throwaway7548 12y ago
  And what if you would move away from that surrounding matter? Or, say launch it away with near light speed, so it would get behind the horizon at some point. How is that situation different from the one in which I've just generated the number and the light cone haven't reached you yet?
  - aaren 12y ago
    > And what if you would move away from that surrounding matter? You can't :) By surrounding matter I meant the rest of your body that isn't neurons, as well as the environment outside your body.
    - throwaway7548 12y ago
      Can't I? What if the state of these poor remaining neurons and the body is scanned, encoded as polarization of a bunch of photons and sent to a receiver far far away? In that case good old environment would definitely end up behind the cosmic horizon.
      - aaren 12y ago
        Then you have implemented teleportation and we have new problems to think about!
        throwaway7548 12y ago
        Oh. Common. No need for any new inventions. Just replace a person [that gets entangled with a particular outcome of a random event (have measured it)] with a simpler organism, say a dog. Or a hamster. Or with a roomba vacuum cleaner ;). Or even with a computer. And we definitely know that a state of a computer can be represented as a bit string encoded on any media. Including polarization of a bunch of photons.
- sfk 12y ago
  ad nauseam
sinesha 12y ago
1. When you tell me the result 6296, my brain becomes only classically correlated with it, not entangled. The source of randomness (whether you got it through a quantum experiment or not) does not matter here, as I am only receiving the classical information. 2. After I forget it completely, all I can say is that I (my current body) am not correlated with the event --- but there is no reason to think of the event as being in my future. It's simply not correlated to me any longer. The process of forgetting means dumping all correlations with an event in the environment. For instance, neurons interact with blood stream that interacts with lungs, passing along those correlations to some air particles. So for my current body, the event never happened, although you might have written the number down and will always remember it. In other words, the past is relative.
- throwaway7548 12y ago
  > So for my current body, the event never happened, although you might have written the number down and will always remember it. In other words, the past is relative. So where this event would be for you? In the future? Again? Yes. Past is definitely relative. Special relativity is very specific about that ;)
  - sinesha 12y ago
    The event is neither in my causal past (it has no influence over the current state of my body) nor in my causal future (I have no influence on it). It's simply uncorrelated with me. If now you remind me of the number again, it becomes part of the causal past of my (new) body. Analogy: if a dwarf dies in a fortress far far away and you don't hear about it, her death is neither in your past nor in your future. You know nothing about her state: in QM, you would say that your brain and her are in an uncorrelated, product state, something like |dunno><dunno| x (|dead><dead| + |alive><alive|)/2 . The x stands for \otimes, tensor product.
- yati 12y ago
  When you say you receive classical information as the outcome of that experiment, what's an example situation in real life when you receive quantum information and do indeed get entangled with it (I mean if at all such a situation ever arises)?

aaren 12y ago

> There are no entanglements any more which link you to that event. Not directly, but the information has spread out from your neurons into the surrounding matter ad nauseum. It's just we can't interpret the information anymore. The event still happened in your past, you just can't see it through your limited human view of reality.

throwaway7548 12y ago
And what if you would move away from that surrounding matter? Or, say launch it away with near light speed, so it would get behind the horizon at some point. How is that situation different from the one in which I've just generated the number and the light cone haven't reached you yet?
- aaren 12y ago
  > And what if you would move away from that surrounding matter? You can't :) By surrounding matter I meant the rest of your body that isn't neurons, as well as the environment outside your body.
  - throwaway7548 12y ago
    Can't I? What if the state of these poor remaining neurons and the body is scanned, encoded as polarization of a bunch of photons and sent to a receiver far far away? In that case good old environment would definitely end up behind the cosmic horizon.
    - aaren 12y ago
      Then you have implemented teleportation and we have new problems to think about!
      - throwaway7548 12y ago
        Oh. Common. No need for any new inventions. Just replace a person [that gets entangled with a particular outcome of a random event (have measured it)] with a simpler organism, say a dog. Or a hamster. Or with a roomba vacuum cleaner ;). Or even with a computer. And we definitely know that a state of a computer can be represented as a bit string encoded on any media. Including polarization of a bunch of photons.
sfk 12y ago
ad nauseam

sinesha 12y ago

1. When you tell me the result 6296, my brain becomes only classically correlated with it, not entangled. The source of randomness (whether you got it through a quantum experiment or not) does not matter here, as I am only receiving the classical information. 2. After I forget it completely, all I can say is that I (my current body) am not correlated with the event --- but there is no reason to think of the event as being in my future. It's simply not correlated to me any longer. The process of forgetting means dumping all correlations with an event in the environment. For instance, neurons interact with blood stream that interacts with lungs, passing along those correlations to some air particles. So for my current body, the event never happened, although you might have written the number down and will always remember it. In other words, the past is relative.

throwaway7548 12y ago
> So for my current body, the event never happened, although you might have written the number down and will always remember it. In other words, the past is relative. So where this event would be for you? In the future? Again? Yes. Past is definitely relative. Special relativity is very specific about that ;)
- sinesha 12y ago
  The event is neither in my causal past (it has no influence over the current state of my body) nor in my causal future (I have no influence on it). It's simply uncorrelated with me. If now you remind me of the number again, it becomes part of the causal past of my (new) body. Analogy: if a dwarf dies in a fortress far far away and you don't hear about it, her death is neither in your past nor in your future. You know nothing about her state: in QM, you would say that your brain and her are in an uncorrelated, product state, something like |dunno><dunno| x (|dead><dead| + |alive><alive|)/2 . The x stands for \otimes, tensor product.
yati 12y ago
When you say you receive classical information as the outcome of that experiment, what's an example situation in real life when you receive quantum information and do indeed get entangled with it (I mean if at all such a situation ever arises)?