QUANTUM INFORMATION Quantum imaging, quantum lithography and the uncertainty principle

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 behaviour of an entangled photon pair. Even though we still have questions with regard to fundamental issues of the entangled quantum systems, quantum entanglement has started to play an important role in practical applications. Quantum lithography is one of the hot topics. We have demonstrated a quantum lithography experiment recently, in which 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.