Are so-called non-local interactions really non-local?

In summary, the non-locality problem in EPR-like experiments arises because the wave function connects two particles in opposite directions, even though they are separated. However, this connection is not a physical propagation at the speed of light, but rather a correlation between the initial state and measurement. The concept of backpropagation on null intervals is a Lorentz variant assumption and not supported by the observation of light pulses propagating in one direction.
  • #1
MeJennifer
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There is something I do not quite understand with regards to the so-called non-locality problem in EPR like experiments.

The wave function propagates at c, so even when two particles, that are part of the same quantum system, move in opposite directions they are still connected. They both travel along a null interval and thus there is a causal connection between the initial state and the measurement.

The same with a single photon, it gets emitted at one place and absorbed at another place but the distance is exactly zero.

What am I missing?
 
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  • #2
MeJennifer said:
The wave function propagates at c, so even when two particles, that are part of the same quantum system, move in opposite directions they are still connected.

I don't think one can in a reasonable way say that "the wavefunction propagates at c", given that it is not defined over normal euclidean (or minkowski) space, but over configuration space.


They both travel along a null interval and thus there is a causal connection between the initial state and the measurement.

If a is a null vector, and b is a null vector, then a - b doesn't need to be a null vector. In the case of EPR, it is a spacelike vector.

Now, of course, you can consider that there is a null-curve linking the events A and B ; however, EVERY two events can be linked by a null curve ! However, you will have to walk this null curve sometimes with a dt > 0, and sometimes with a dt < 0.

So, yes, if you allow for "backward propagation of light signals" then every event is local to every other event. But that's not the idea, in general, although certain people look upon it that way (although I'm not an expert, the transactional view on QM does something of the kind I think).
 
  • #3
How do you demonstrate backpropagation on null intervals? :confused:
That seems to me a Lorentz variant assumption.
 
  • #4
MeJennifer said:
How do you demonstrate backpropagation on null intervals? :confused:
That seems to me a Lorentz variant assumption.

Well, if Joe sends out a light pulse to Jack, I think that all observers can testify about the direction in which the lightpulse propagated. Nobody will see the lightpulse propagate from Jack to Joe.

This comes about because you cannot transform a lorentz vector (t,x,y,z) with t>0 into one with t<0 through a continuous lorentz transformation, EVEN when the vector is lightlike.
 

1. What are non-local interactions?

Non-local interactions refer to any type of interaction between two or more particles that cannot be explained by the laws of classical physics. These interactions are often described as being "non-local" because they do not follow the principles of locality, which state that objects can only influence each other if they are in close proximity.

2. Are non-local interactions really non-local?

The term "non-local" can be misleading, as it implies that these interactions occur at a distance without any physical connection between the particles. However, in quantum mechanics, non-local interactions can be explained by the concept of entanglement, where particles become connected in a way that their behavior is correlated even when they are separated by large distances.

3. How are non-local interactions different from local interactions?

Local interactions are those that can be explained by the laws of classical physics, where objects must be in close proximity to influence each other. Non-local interactions, on the other hand, cannot be explained by these laws and often involve particles that are entangled or connected in a way that their behavior is correlated regardless of distance.

4. What evidence supports the existence of non-local interactions?

One of the main pieces of evidence for non-local interactions is the phenomenon of quantum entanglement. This has been observed in numerous experiments, including the famous "EPR paradox" experiment, where two entangled particles were found to influence each other's behavior instantaneously despite being separated by a large distance.

5. How do non-local interactions impact our understanding of the universe?

Non-local interactions have significant implications for our understanding of the universe, especially in the field of quantum mechanics. They challenge our classical understanding of cause and effect, and suggest that there may be underlying connections between seemingly separate particles. Non-local interactions also play a crucial role in technologies such as quantum computing and cryptography.

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