Student Manual

One of the most astounding and bewildering depictions of quantum mechanics is the single- particle interference experiment. If a source that emits only one particle (such as photons or electrons) at a time, is used in a classic double slit experiment, an interference patterns will emerge. This pattern is built up over multiple passes of identical particles. Interestingly, the pattern could be switched on and off even after light has emerged from the interferometer.

The Mach-Zehnder interferometer is a useful device for exploiting the wave nature of light and observing various aspects of interference. The goal of this experiment is to familiarize students with this kind of an interferometer. We will observe interference of light, and see conditions under which interference can be washed out, and ultimately recovered.

Sample ResultsErasure and recovery of which-path information inside a Mach-Zehnder interferometer
Variation of intensity pattern with the post-interferometer polarizer
Variation of optical intensity with the relative angle between the polarizers placed inside the arms of the interferometer
Fringes change their visibility as polarizers between the arms of the interferometer change their relative angles
Experiment Code2.21

Further Readings and References

Pictorial Procedure

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