A signature experiment highlighting the wave-particle duality, uncertainty, delayed-choice and quantum computing is developed at the Physlab. It will introduce students to the concepts using classical light from a laser. For more details visit the experiment website here.
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 Results||Erasure and recovery of which-path information inside a Mach-Zehnder interferometerVariation of intensity pattern with the post-interferometer polarizerVariation of optical intensity with the relative angle between the polarizers placed inside the arms of the interferometerFringes change their visibility as polarizers between the arms of the interferometer change their relative angles|
Further Readings and References
- There are no particles, only fields American Journal of Physics , A. Hobson , 81 211 , (2013).
- Delayed choice quantum eraser experiment explained , https://www.youtube.com/watch?v=U7Z_TIw9InA , (2014).
- Chapter 6 Physics of Light and Optics , http://optics.byu.edu/textbook.aspx , J. Peatross and M, Ware 143-168 , (2015).
- Teaching quantum theory in the introductory course The Physics Teacher , A. Hobson , 34 202 , (1996).
- Understanding walking the beam , http://laser.physics.sunysb.edu/~simone/mini-project/ , S. Agha and D. Minkin , (2007).
- Single photon quantum erasing European Journal of Physics , T.L. Dimitorva and A. Weis , 31 5 , (2010).
- Quantum computing with photons Journal of Physics B: Atomic, Molecular, Optical Physics , S. Barz , 48 083001 , (2015).
- A do-it yourself quantum eraser Scientific American , R. Hillmer and P. Kwiat 90 , (May 2007).
Optical tunneling is demonstrated by frustrated total internal reflection.
- A green laser diode (from a laser pointer) falls on a glass prism. The angle of incidence is greater than a critical angle, resulting in light being totally internal reflection.
- There is evanescent light leaking from the prism. But this light is difficult to tap off, unless a second prism is placed really close to the first one.
the second prism is almost conjoined with the first prism using an index matching fluid (Cargille’s BK 7 Matching Liquid).
- The fluid is able to mate the prisms really well, yet it keeps a small gap between the prisms. Light can tunnel across this classically forbidden region and transmit into the second prism. Total internal reflection has been frustrated.