One of the most surprising consequences of quantum mechanics is the entanglement of two or more distance particles. The 'ghost' image experiment demonstrated the astonishing nonlocal behavior of an entangled photon pair. Even though we still have questions in regard to fundamental issues of the entangled quantum systems, quantum entanglement has started to play important roles in practical applications. Quantum lithography is one of the hot topics. We have demonstrated a quantum lithography experiment recently. The experimental results have beaten the classical diffraction limit by a factor of two. This is a quantum mechanical two-photon phenomenon but not a violation of the uncertainty principle.
Yanhua Shih, Yanhua Shih,
"Quantum imaging, quantum lithography and the uncertainty principle", Proc. SPIE 4821, Free-Space Laser Communication and Laser Imaging II, (9 December 2002); doi: 10.1117/12.451055; https://doi.org/10.1117/12.451055