Surface shape measurement by using entanglement photon state (the 2nd report)

interference and distance measurement

Abstract

Surface of x-ray mirror or sub-wavelength device need to be measured in a depth precision of nano-order. Interferometry is widely used in surface shape measurement but its precision in depth is limited by the wavelength of light source, with a tens-nano-order. The purpose of this paper is to develop a new interferometry with nano-order precision for surface shape measurement, using entanglement photon state (EPS) as light source. Wavelength of N photon entanglement state is demonstrated N times shorter than the wavelength of a single photon, according to the definition of de-Broglie wave. Thus, by using EPS as light source, interferometry can have a higher precision, up to nano-order. In the last paper, the generation of EPS (N = 2) is done, by two-photon-interference. This paper will report a distance measurement with higher precision than single photon state. The distance is measured by the interference of EPS with a high repeatability.