Communication faster than light or where is my mistake?

Click For Summary

Discussion Overview

The discussion revolves around the possibility of communicating faster than light using entangled photons and polarizers. Participants explore the implications of wave function collapse and the potential for information transfer between two observers, Alice and Bob, through a series of proposed experiments and measurements.

Discussion Character

  • Exploratory
  • Debate/contested
  • Technical explanation

Main Points Raised

  • One participant proposes a scenario involving entangled photons and polarizers, suggesting that Alice's manipulation of her polarizer could instantaneously affect the polarization of Bob's photon, potentially allowing for faster-than-light communication.
  • Another participant asserts that Bob cannot experimentally separate the outcomes of the photons in a way that would allow for faster-than-light communication.
  • A later reply suggests a method involving amplifying single photons and using multiple polarizers at different angles to determine the initial polarization, questioning if this could work despite previous assertions.
  • Another participant counters that spacelike separated operators commute, indicating that no measurement on one photon can influence the outcome of another photon faster than light, regardless of the proposed methods.

Areas of Agreement / Disagreement

Participants express disagreement regarding the feasibility of faster-than-light communication through the proposed methods. While some explore potential experimental setups, others firmly reject the possibility based on established principles of quantum mechanics.

Contextual Notes

Limitations include assumptions about the behavior of entangled photons and the implications of wave function collapse. The discussion does not resolve the mathematical or conceptual challenges posed by the proposed scenarios.

jakeliuns
Messages
2
Reaction score
0
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:

Alice...Source........Bob

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.

Alice...Source...X...Bob

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?
 
Science news on Phys.org
jakeliuns said:
If Bob can experimentally separate these 2 cases
But he can't.
 
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?
 
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.
 

Similar threads

  • · Replies 7 ·
Replies
7
Views
2K
  • · Replies 55 ·
2
Replies
55
Views
4K
  • · Replies 52 ·
2
Replies
52
Views
7K
  • · Replies 19 ·
Replies
19
Views
1K
  • · Replies 4 ·
Replies
4
Views
2K
  • · Replies 6 ·
Replies
6
Views
2K
  • · Replies 45 ·
2
Replies
45
Views
7K
  • · Replies 28 ·
Replies
28
Views
2K
  • · Replies 7 ·
Replies
7
Views
2K
  • · Replies 16 ·
Replies
16
Views
3K