Does the photon have refused glimpse?

Can photons be able to say that they are about to be seen by someone? John Wheeler first made a hypothesis to explain this singularity by approaching a new trend in the double-slit experiment nearly 30 years ago. Today, physicists in France have for the first time carried out experiments to demonstrate this (the paper published in Science 315 996, 2007).

The famous double-slit experiment applied to photons almost highlights the observer's mysterious influence in quantum mechanics. In this experiment, a single photon illuminates at one point on the screen, preventing the space between the wall containing two slots. If someone just neglected not to check the slot that the photon passed, the photon would interfere itself (assuming it passed through two slits like a wave).

But if we record the slots carefully, the interference will disappear, and each photon will pass through the gap as the transmission of a single particle. In 1978, however, John Wheeler showed that a photon could somehow know whether an observation could lead to a change in its behavior such as a wave or a corresponding particle. To test this possibility, he assumed an experiment in which the decision to observe photons was only made after the photon was emitted.

Figure 1. Photo of the experimental system (Photo: physicsweb.org)

Recently, the team of Jean-François Roch and colleagues at the École Normale Supérieure de Cachan (Cachan University of Education, France) for the first time correctly verified the experimental ideas of Wheeler. The group replaced 2 slots (as Young's 2-slot interference experiment - this device can cause inconvenience) by splitting the beam into 2 passes (see Figure 2). These transmissions directly lead to two recorders, allowing a clear observation of the path that each photon has passed. However, physicists have also devised an automated system that can randomly insert a beam splitter at every moment. When this beam splitting system is placed, the observer cannot know the path of the photon.

Figure 2. Beam splitter. (Photo: physicsweb.org)

When there is no beam splitter, the photon will pass through or follow this path, or follow the remaining path as a particle. But when there is a beam splitter, the detetors have recorded interference - that is, the photons carry the behavior of one wave and pass through both lines simultaneously. However, not quite the same as the previous 2-slot experiments, the system can make a decision to observe after the photon is transmitted to one line or another, or both. Therefore, if a source converges " secretly " to photons, it must send faster than the speed of light, which violates the principle of relativity.

"Because of this coercion, we can be sure that the photon does not know what the outcome is at the interferometer when they enter," - Roch said. "This is further increasing the" tension "between quantum mechanics and relativistic mechanics ".

The Doctrine of Independence

According to Physicsweb.org, Vietnam Physics