Measurement of the Photonic de Broglie Wavelength of Entangled Photon Pairs Generated by Spontaneous Parametric Down-Conversion

Using a basic Mach-Zehnder interferometer, we demonstrate experimentally the measurement of the photonic de Broglie wavelength of entangled photon pairs (biphotons) generated by spontaneous parametric down-conversion. The observed interference manifests the concept of the photonic de Broglie wavelength. We also discuss the phase uncertainty obtained from the experiment.

Figure 1

Schematic experimental setup of the biphoton interference. KN: ${\mathrm{K}\mathrm{N}\mathrm{b}\mathrm{O}}_3$ crystal, $\mathrm{B}\mathrm{S}1\sim 3$: beam splitters, IF: interference filters, APD: avalanche photodiodes.

Figure 2

Coincidence-photon-counting rate detected at the two output ports of BS1 as a function of the optical path-length difference ($\Delta L_1$) between the two paths from KN and BS1 in Fig. 1. Open circles indicate experimental data, and the solid curve is a fitted function that assumes the observed photons have a rectangular spectral shape.

Figure 3

Interference patterns in the one-photon (upper) and two-photon (lower) counting rates at a path-length difference of around $0\mu \mathrm{m}$.

Figure 4

Interference patterns in the one-photon (upper) and two-photon (lower) counting rates at a path-length difference of around $400\mu \mathrm{m}$.