# B Pseudorandomness of correlation

#### entropy1

Suppose we have a source of polarization-entangled photons, that fires pairs of photons in opposite directions at two detectors with orientation-adjustable polarizationfilters in front of them. Obviously, there is a correlation between the orientation of the respective filters and the joint detection correlation. Equally obvious is that the measured correlation is cos2(β-α), with α and β the angles of the respective filters.

So, in my eyes this seems to suggest that the distribution of the detection of the photons at either side gets at least partly influenced, or even determined, by the orientation of the filters or the quantitative value of the correlation (cos2(β-α)). Mind you, the distribution of the detections! This can happen at the one side, the other side, or both sides, we don't know.

Does the fact that the distribution of the detections gets consequently and lawfully 'affected' not suggest that the detections are not completely random, but rather pseudorandom? That is, to consistently constitute a certain correlation between the detections at both sides, we have to have more than 'pure' random distributions at each end?

NOTE: It seems to me a relation between space (orientation of the filters) and time (the moment of detection yes/no), in relation to quantization (that we get a correlation in the first place).

Last edited:
Related Quantum Physics News on Phys.org

#### DrChinese

Gold Member
Does the fact that the distribution of the detections gets consequently and lawfully 'affected' not suggest that the detections are not completely random, but rather pseudorandom? That is, to consistently constitute a certain correlation between the detections at both sides, we have to have more than 'pure' random distributions at each end?

NOTE: It seems to me a relation between space (orientation of the filters) and time (the moment of detection yes/no), in relation to quantization (that we get a correlation in the first place).
I don't see how your idea relates to the difference between pseudo-randomness and true randomness. I associate pseudo-randomness (in this context) with there existing a cause of an outcome.

There are reasons to suggest there is a "cause" to outcomes (see EPR). But there are also reasons to reject those (see Bell).

#### entropy1

I don't see how your idea relates to the difference between pseudo-randomness and true randomness. I associate pseudo-randomness (in this context) with there existing a cause of an outcome.
I would say the orientation of the filters has an influence on the distribution. If you could call that a 'cause', I don't know...

On the other hand, maybe more should be taken into account and I am oversimplying this matter, which would be plausible.

#### entropy1

In a way, one could see the wavefunction of the entangled pair as a 'cause' for the correlation, could it? However, this seems to me an easy way out.

#### Nugatory

Mentor
In a way, one could see the wavefunction of the entangled pair as a 'cause' for the correlation, could it
"In a way..." seems too weak to me, as the correlation is clearly implied by that wavefunction - an ensemble of particles in the singlet state has to produce those correlations. You prepare a system in a state such that something will happen, then that something happens.... There's no great surprise here.
However, this seems to me an easy way out.
That is a matter of personal taste. You may not be satisfied with that resolution, but the minimal statistical crowd generally is.

#### entropy1

"In a way..." seems too weak to me, as the correlation is clearly implied by that wavefunction - an ensemble of particles in the singlet state has to produce those correlations. You prepare a system in a state such that something will happen, then that something happens.... There's no great surprise here.

That is a matter of personal taste. You may not be satisfied with that resolution, but the minimal statistical crowd generally is.
The joint wavefuntion, the singlet state, consists of two product states in superposition defined to be opposite to each other right? So, unless someone could explain to me why not, it seems to me as if correlation in terms of states is rather defined than implied.

"Pseudorandomness of correlation"

### Physics Forums Values

We Value Quality
• Topics based on mainstream science
• Proper English grammar and spelling
We Value Civility
• Positive and compassionate attitudes
• Patience while debating
We Value Productivity
• Disciplined to remain on-topic
• Recognition of own weaknesses
• Solo and co-op problem solving