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Interference or non-interference

  1. Sep 6, 2011 #1
    We sent an ensemble of single photons through an adjusted Mach-Zender interferometer to get interference. The resulting interference directs all the photons into detector 1. Subsequently, we loose the fixed two mirrors at their original positions in Mach-Zender interferometer and sent the single photons emitted from the light source again. Then we record which detector (detect 1 or 2) would receive the signals. Finally, we replace the two mirrors to their original position and repeat this process of emission and recoding. We statistic the signals the detectors received to confirm whether interference happened. If the signals were detected only by detector 1, the interference happen; if the signals were detected by detector 1 or 2 stochastically, the interference did not happen.
    Thus, the results of this experiment will be interference or non-interference. However, the interference will not happen according to the quantum mechanics, because we will not get the interference when we detect the path photon pass through:
    We calculate the momentum of the mirror pre and post- reflection of photons to justify which paths the photons choose through observing the changes in the momentum of mirror. There was the opinion that to measure the recoil to accuracy Δp the momentum of the mirrors we must be known to this accuracy before the photon passes through. This introduces an uncertainty in the position of the mirrors and therefore the position of the mirrors equal to h / Δp, and if the mirrors' momentum is known precisely enough to measure the recoil, the mirrors' position is uncertain enough to destroy the interference.
    We know that the momentum of mirror before the photon passing through the mirror can be detected precisely, while the position of the mirror can not be confirmed simultaneously. However, it did not mean that the process of detection change the original position of the mirror. We will not get interference if the position of the mirror changed. Thus, when the photons emitted from the light source were reflected by the mirror, we get interference because the position of the mirror did not change. After the reflection, we measured the momentum of the mirror again to obtain the difference in mirror’s momentum. Finally, we can know that which mirror reflected the photon and which path the photon passed through. The most important, the interference will not be influence. In conclusion, we know the path the photon passed through and have no effect on interference simultaneously.
    If the process of momentum measure changed the original position of the mirror, the interference will not happen.
  2. jcsd
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