Single Photon Interference

at Hobart and William Smith Colleges dept. of Physics

Fall 2019

The wave-particle duality of light has been investigated in a variety of ways. This experiment seeks to show a wave property of light, diffraction, with quantized particles of light, thus showing that light behaves both as a wave and a particle.

A high-intensity laser and a filtered incandescent light were used as nearly mono-chromatic sources. Both sources then were put under single and double slit diffraction. The intensities were then measured in finite widths across appropriate detectors for each source: a photodiode for the laser and a photomultiplier (PMT) for the incandescent bulb.

The PMT is able to measure the rate of individual photons arriving at the detector. With a known chamber length, it can be shown that each photon is traveling one at a time, and still producing a diffraction pattern.

Below the paper of the result can be found.

A plot showing the double slit diffraction data collected (blue) and the fitted Fraunhofer diffraction pattern (red). The source was a incandescent bulb that was dim enough for single photon emission.

Single Photon Interference Paper