The Experiment

A beam of light shines on the projection screen. Filters $A$, $B$, and $C$ are polarised horizontally, at $45^{0}$, and vertically, respectively, and can be placed so as to intersect the beam of light.

First, insert a filter $A$. Assuming that incoming light is randomly polarised, the intensity of the output will have half the intensity of the incoming light. The outgoing photons are now all horizontally polarised.

Figure 1: Filter $A$ inserted

The function of filter $A$ cannot be explained as a "seive" that only lets those photons pass that happen to be already horizontally polarised. If that were the case, few of the randomly polarised incoming electrons would be horizontally polarised , so we could expect a much larger attenuation of the light as it passes through the filter.
Next, when filter $C$ is inserted, the intensity of the output drops to zero. nine of the horizontally polarised photons can pass through the vertical filter. A Seive model could explain this behavior.

Figure 2: Filters $A$ and $B$ inserted

Finally, after filter B is inserted between $A$ and $C$, a small amount of light will be visible on the screen, exactly one eighth of the original amount of light.

Figure 3: Filters $A$, $B$ and $C$ inserted

Here we have a non-intuitive effect. Classical experience suggests that adding a filter should only be able to decrease the number of photons getting through. How can it increase it?