Bi-photon de Broglie Wavelength
Measuring the wavelength of an entangled pair of photons (red circles)
made inside a potassium-niobium (KN) crystal by parametric down conversion
of an incoming photon (blue circle). After encountering an initial beam
splitter (BS1), the red photons move together along either path 1 or
path 2, whose lengths can be adjusted (delta L). Along they way they
encounter other beam splitters, and finally pass through interference
filters (IF) and enter avalanched photodiodes (APD). (Courtesy Osaka
University)
