Does entangled polarized photon get through filter?

Click For Summary

Discussion Overview

The discussion revolves around the behavior of entangled photons when passing through polarized filters, specifically addressing the outcomes based on the polarization states of the photons and the implications of their entanglement. The scope includes theoretical considerations and conceptual clarifications regarding quantum mechanics and polarization.

Discussion Character

  • Exploratory
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant proposes that if photon A passes through a vertically polarized filter, photon B becomes vertically polarized as well, leading to photon B being blocked by a horizontal filter.
  • Another participant asserts that the relationship between the entangled photons guarantees that one will pass through its filter while the other will not, regardless of the order in which they encounter the filters.
  • A participant questions whether photon B remains unpolarized if photon A is blocked by the vertical filter, suggesting that both photons could potentially be blocked.
  • One participant clarifies that photon A's interaction with the polarizer determines the polarization of both photons after the interaction, implying that photon B cannot remain unpolarized if photon A is blocked.
  • Another participant points out a potential misunderstanding regarding the initial polarization state of the entangled photons, suggesting that the answers assume a definite polarization rather than an initially unpolarized state.
  • A later reply elaborates that the polarization state of the photons can be viewed as a superposition, which collapses to a definite state upon interaction with the polarizer.

Areas of Agreement / Disagreement

Participants express differing views on the initial polarization state of the entangled photons and the implications of their interactions with the filters. There is no consensus on whether both photons can be blocked simultaneously, and the discussion remains unresolved regarding the assumptions about the initial polarization.

Contextual Notes

Participants highlight limitations in the assumptions regarding the initial polarization states of the photons and the implications of their entanglement, which may affect the interpretation of the outcomes when interacting with the filters.

entropy1
Messages
1,232
Reaction score
72
Suppose we have a creation point C where two entangled photons A en B are produced. 1m in the direction of A is a vertically polarized filter V. 2m in the direction of B is a horizontal polarized filter H.

Now, I understand that when photon A strikes filter V, it either gets blocked or gets through at a 50/50 rate. If, however, photon A gets through the filter, it becomes vertically filtered, and so is photon B. So photon B then gets blocked by filter H.

Now I wonder what happens if photon A gets blocked by filter V. Does photon B remain unpolarized, thereby retaining the 50/50 percent chance of getting blocked by filter H? So, is it possible that both photons get blocked at any given time?
 
Physics news on Phys.org
No, their relationship guarantees that one will get through and one will not.

By the way: there is no experimental sense in which the order of the photons encountering their respective polarizing filters matters. Whether it is A's being 1 meter and B's being 2 meters away, or vice versa, outcomes appear the same.
 
  • Like
Likes   Reactions: bhobba
entropy1 said:
Now I wonder what happens if photon A gets blocked by filter V. Does photon B remain unpolarized, thereby retaining the 50/50 percent chance of getting blocked by filter H? So, is it possible that both photons get blocked at any given time?

No. A's interaction with the polarizer is: absorbed if horizontally polarized, transmitted if vertically polarized. That's sufficient to determine the polarization of both A and B after the interaction.
 
I have a problem with this thread: OP seems to assume initially unpolarized entangled photons (allthough the title of this thread seems to suggest otherwise), but the answers assume a kind of definite either vertical or horizontal polarization, don't they ?
 
Yes, my mistake (the title).
 
forcefield said:
I have a problem with this thread: OP seems to assume initially unpolarized entangled photons (allthough the title of this thread seems to suggest otherwise), but the answers assume a kind of definite either vertical or horizontal polarization, don't they ?

They only acquire that definite polarization when one of them encounters the polarizing filter, and then when we say "horizontal" or "vertical" we mean with respect to angle of the polarizer.

Any polarization state can be written as a superposition of horizontal and vertical polarization about any axis; interaction with a polarizer on a given axis causes the superposition to collapse to one of those two states.
 

Similar threads

Graduate What happens when entangled photons are split into different paths?
  • · Replies 41 ·
2
Replies
41
Views
7K
High School Why do photon polarization experiments show similar outcomes in different situations?
  • · Replies 11 ·
Replies
11
Views
3K
Undergrad How does a band pass filter increase the time of arrival of photons?
  • · Replies 2 ·
Replies
2
Views
1K
Graduate How produce twin photons in practice?
  • · Replies 3 ·
Replies
3
Views
1K
High School Probability of a photon passing through a filter
  • · Replies 5 ·
Replies
5
Views
2K
Undergrad What happens when circular polarization meets a diagonal polarizer?
  • · Replies 20 ·
Replies
20
Views
4K
Undergrad Problem with the polarization of entangled photons
  • · Replies 7 ·
Replies
7
Views
2K
High School Exactly why FTLC is impossible with entangled photons?
  • · Replies 40 ·
2
Replies
40
Views
5K
Undergrad How to distinguish between diagonal vs horizontal/vertical polarization?
  • · Replies 15 ·
Replies
15
Views
4K
High School A couple of questions about photons and superposition..
  • · Replies 6 ·
Replies
6
Views
2K