In this experiment, we want to push the delayed choice quantum eraser a little bit further. While navigating forums and FAQs on different website, we saw so many theories people create around the experiment. What if we block one of the path. What if a fly look at the beam and not me. What if the detector is not plugged. And so many more.
All of the ideas of those "What if" is to figure out what really is a detection. If someone else looks at D2 but not me, are we going to see the same results. Or if a fly or a tree detects the photons, what would happens. Actually, the answer is simple, when we look at coincidence, we need to put the two signal togheter. Any of those situation doesn't allow you to count coincidence, so no interference. Plus, there is no way one could destroy the information stored in a photon. it might change form if a photon is absorbed in a wall, but information will never truly be lost.
In this section, we will do two of these scenarios. The first one is blocking the photon with a wall on the path of D2. The second one is to measure with detector D2 unplugged. We will finish this section with a FAQ with a few more "What if" we found on comments on video and explain their result.
You can download all our data here:
There are 7 columns, The first two are the angle on the polarizers. The thrid column is the step of the actuator. One step is 1μm. Next, there's a column indicating which sweep the actuator is at. The last three columns are the counts on the detector. The first for D1 (on the double slits path), the second for D2 and the third is the coincidences between D1 and D2.
At each step of the actuator, we take several points to be able the have an average and a standard deviation. And we do a sweep of all step a few times to be able to average even more and reduce errors. All the step were saved in different files.
Let's take the time to analyse those graphics. We see the plot for detector A are always following the diffraction curve. Just like in all the test in experiment 5, we will never see interference on this plot. On the coincidence plot, we don't see anything at all. In the graph for the wall, there is a wall roght in front of D2, of course we don't get a signal. We still see a very small number of coincidence happening. There might be light still penetrating from another angle or from different source. It is experimental error. And on the plots with D2 unplugged, we see a clear 0 coincidence, which is obvious.
The way we present the results of the experiment might seems a little obvious. If the detctor is not working, then we don't get any signal. Let's try to go a little deeper in these experiments and see what else we can conclude on.
Now, the reel question is why isn't tere any interference on the bottom path? (By the way, we should have had this question in experiment 5.3, but we did le)
