Steering the polarization of entangled photons

[kurt101]

TL;DR

I want to be convinced one way or another on whether entangled photons can be steered or not in some realistic causal way.

The following is a diagram of an EPR thought experiment using photons that uses the same type of components as described in this paper http://www2.optics.rochester.edu/~stroud/cqi/rochester/UR19.pdf

Would you detect any photons at the right detector?

I want to be convinced one way or another on whether entangled photons can be steered or not in some realistic causal way. My thought process is if there are no photons detected at the right detector then the polarizer on the left that allows Θ polarized photons through has no instant causal effect on the polarization of its entangled photon partner on the right side.It is my understanding that the analyzer loop with no blockers that looks like:

has no effect on the experiment, but I include it in the diagram to make the sequencing and path lengths between the left and right sides clear.

 

[DrChinese]

1. Would you detect any photons at the right detector?

2. I want to be convinced one way or another on whether entangled photons can be steered or not in some realistic causal way.

3. ... path lengths between the left and right sides clear.

1. No, because both the x and the y channels are blocked. The middle loop does not restore the earlier entangled state, it simply transmitting the x photons.

2. You can steer an entangled photon into a basis by measuring it, but you cannot steer the value on that basis per se.

3. Path length does not play a factor per se.

 

[kurt101]

2. You can steer an entangled photon into a basis by measuring it, but you cannot steer the value on that basis per se.

Thanks! I should have known that and I can see now it does not say anything about my own question about realistic causality which I suppose is good because I am still hopeful someday this will all make sense

 

[kurt101]

2. You can steer an entangled photon into a basis by measuring it, but you cannot steer the value on that basis per se.

Trying again:

In this diagram, will there be any photons detected at the right detector?

My thought process is that the measurement on the left side is made between when the y polarized photons are blocked and when the x polarized photons are blocked. So if photons are detected at the right detector, the measurement at the left detector had an instant effect on the polarization of photons on the right path.

Thanks

 

[DrChinese]

View attachment 257593

1. In this diagram, will there be any photons detected at the right detector?

2. My thought process is that the measurement on the left side is made between when the y polarized photons are blocked and when the x polarized photons are blocked. So if photons are detected at the right detector, the measurement at the left detector had an instant effect on the polarization of photons on the right path.

1. No, there are no photons getting through on the right side, regardless of what happens on the left side.

a. The right side loses its entanglement with the left once the right side's first polarizer (with blocked y) is encountered.
b. And... the light side loses its entanglement with the right once the left side's second polarizer (with blocked channel) is encountered.

As mentioned path length is not a factor and there is no saying which (if either) a. or b. occurs first. So there won't be any particular EPR correlations.