This is a pretty basic question I think. But it's quite hard to find actual experimental results on the web (or maybe I don't know the right keywords).
I'm new to quantum mechanics and want to understand its effects by seeing the results of experiments.
Assume we have an entangled photon source that emits photons in two directions so their polarization plane is the same*. Each of them pass through a polarizer. And the polarizers have an angle $\alpha$ between their filter planes.
I calculated the chance in classical way. Due to the Malus' law the chance that the photon passes the polarizer is $\mathrm{cos}^2 x$, where $x$ is the angle between the polarizer filter's and the photon's polarization plane.
So the chance that both photons pass through their respective polarizers is: $(\mathrm{cos}^2 x)(\mathrm{cos}^2 (x+\alpha))$. $x$ is a random angle. So to get the general chance I must integrate over $x$ between $0$ and $2\pi$, and take the average by dividing by $2\pi$. I got:
$$\frac{\mathrm{cos}(2\alpha)+2}{8}$$
So this would mean 3/8 chance of pass when the two polarizers have the same and angle have 1/8 chance when they are perpendicular to each other.
Interestingly I also calculated what's the chance that photons fail both filters, so doing the previous computation on $(1-\mathrm{cos}^2 x)(1-\mathrm{cos}^2 (x+\alpha))$, I got the very same formula (I guess not without a reason).
Since these kinds of experiments are performed using coincidence counters and polarizing prisms (so we can count the cases when both of them pass or fail). My prediction would suggest a chance of coincidence that varies between 1/4 and 3/4 with the polarization angle.
That was the classical approach.
Now my questions:
- What probabilities does quantum mechanics predict? Is there 100% match when the polarizers are aligned?
- What did we actually observed when this measurement was performed experimentally?
* For simplicity. I guess in real life the planes would probably be perpendicular. But we can bias the polarizer's angle accordingly.