Superresolving Phase Measurement with Short-Wavelength NOON States by Quantum Frequency Up-Conversion
Zhi-Yuan Zhou, Shi-Long Liu, Shi-Kai Liu, Yin-Hai Li, Dong-Sheng Ding, Guang-Can Guo, Bao-Sen Shi · Physical Review Applied · 2017
Precise measurement is at the heart of physical science, and taking advantage of quantum effects, where practicable, affords sensitivity beyond the reach of classical methods. Rather than increasing photon number to reduce the de Broglie wavelength and achieve superresolution via quantum optics, the authors use quantum frequency up-conversion to realize 525-nm maximally entangled photons. This two-photon NOON state offers a visibility better than the threshold for beating the standard quantum limit, and could be used for high-precision metrology in many applications.