Observation of the four-photon de Broglie wavelength by state-projection measurement
Fang‐Wen Sun, Bi‐Heng Liu, Yun‐Feng Huang, Z. Y. Ou, Guang‐Can Guo · Physical Review A · 2006
A measurement process is constructed to project an arbitrary two-mode $N$-photon state to a maximally entangled $N$-photon state. The result of this projection measurement shows a typical interference fringe with an $N$-photon de Broglie wavelength. For an experimental demonstration, this measurement process is applied to a four-photon superposition state from two perpendicularly oriented type-I parametric down-conversion processes. Generalization to the projection measurement of an arbitrary $N$-photon state can be easily made and may have wide applications in quantum information. As an example, we formulate it for precision phase measurement.