Communication faster than light or where is my mistake?

In summary, the conversation discusses the possibility of communicating faster than light using entangled photons. The setup involves Alice, Bob, and a source of entangled photons, and the experiment shows that information from Alice to a certain point can travel instantly, while information from that point to Bob can only travel at the speed of light. However, it is concluded that it is not possible to use this to communicate faster than light due to the principle of spacelike separated operators commuting. Personal speculation is also deemed irrelevant to the discussion.
  • #1
Hello, here is some reasoning how I got possibility to communicate faster than light.
Likely somewhere are mistakes, but I can not find them by myself.

Let's consider very simple setup with observers Alice, Bob and a source of entangled photons in-between of them like so:


Let's say distance (Source........Bob) is twice as (Alice...Source)

Also let's say both observers have polarizers oriented equally, let's say vertically.

Now let's begin the experiment. Source emits pairs of entangled photons.
Left photon goes to Alice and right photon goes to Bob.
Let's name them like photon (L) and photon (R).

When photon (L) hits Alice's polarizer wave function collapse is happening.
But photon (R) is still traveling. Let's say it is at point X during the collapse of mentioned wave function.


Because of wave function collapse right photon (R) gets defined polarization.
As I mentioned earlier both polarizers are oriented vertically,
so the photon (R) at point X could get vertical or horizontal polarization
(exactly the same polarization like photon (L) who just passed Alice's polarizer).

So like a sequence both photons will act equally at both polarizers.

Until now nothing strange was detected.
But let's say distances are big enough.
Now let's Alice rotates her polarizer by 45 degree.

When next photon (L) will hit this polarizer opposite photon (R) also will get diagonal polarization at mentioned point X. This polarization will be diagonal like so “/” or like so “\”

Now we see that some sort of information from Alice to point X travels instantly
and only from point X to Bob information travels with velocity c.
Ones again if Alice puts her polarizer vertically Bob will get 50% of vertically polarized
photons and 50% horizontally polarized photons.
But if Alice turns her polarizer by 45 degree Bob will get 50% of photons by this “/” diagonal polarization and 50% by this “\” diagonal polarization.

The question is can Bob separate which photons are coming now,
with polarization like so “|”and “--”
or like so “/” and “\” ?

If Bob can experimentally separate these 2 cases he can get information from Alice faster than light, because information about the angle of Alice's polarizer travels instantly from her to point X.
What do you think?
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  • #2
jakeliuns said:
If Bob can experimentally separate these 2 cases
But he can't.
  • #3
Likely you are right, but still let's try to invent some measuring procedure to separate mentioned 2 cases.
What if Bob obtain single photons from incoming beam and send them to amplifier.
Let's say from 1 single photon he gets 1000 of them. All of them will have the same polarization.

Now Bob splits these photons into 10 (or more) groups and each group of photons sends to a separate polarizer. Let each polarizer has different angle of polarization.

From the total outcome how all these 1000 photons have passed all polarizers could be possible to find out polarization of the initial photon Bob was measured.

Am I right or maybe here are some more mistakes?
  • #4
It doesn't work this way. Spacelike separated operators commute, so there is simply no possible way that anything done on one photon will affect the outcome of a measurement of another photon faster than light. It doesn't matter if you use an amplifier a beam splitter or whatever.

Personal speculation is not permitted. Thread closed.

1. How is it possible to communicate faster than the speed of light?

Currently, it is believed that nothing can travel faster than the speed of light. This is based on Einstein's theory of relativity, which states that the speed of light is the maximum speed at which all matter and information can travel. Therefore, it is not possible to communicate faster than the speed of light.

2. Is there any evidence of communication faster than light?

No, there is no scientific evidence of communication faster than the speed of light. All experiments and observations have shown that the speed of light is the fastest speed at which information can travel.

3. What is the concept of entanglement and does it allow for faster-than-light communication?

Entanglement is a phenomenon in quantum physics where two particles become connected and can affect each other's properties, even when separated by great distances. However, this does not allow for faster-than-light communication as it does not involve the transfer of information, but rather a correlation between the two particles.

4. Are there any proposed theories or technologies that could potentially allow for faster-than-light communication?

There are some theoretical concepts, such as wormholes or tachyons, that have been proposed as means of faster-than-light communication. However, these are still highly speculative and have not been proven to exist or be possible.

5. What are the implications of faster-than-light communication if it were possible?

If faster-than-light communication were possible, it would completely change our understanding of physics and the laws of the universe. It could potentially lead to the possibility of time travel and could have major implications for our current models of space and time. However, until there is scientific evidence to support it, faster-than-light communication remains a topic of science fiction rather than fact.

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