The Role of Entanglement in Quantum Lithography
Sun Kyung Lee, Hai-Woong Lee · Journal of the Physical Society of Japan · 2008
We investigate the origin of the resolution improvement beyond the classical diffraction limit in quantum lithography. We show that the degree of the resolution improvement persists even when the pure entangled state of light initially prepared (the NOON state) is transformed to a mixed entangled state caused by phase and amplitude damping, regardless of the degree of entanglement remaining in the state. We also show that the resolution improvement beyond the classical diffraction limit can be achieved with a particular class of separable states of light. The resolution improvement in this case can be traced to entanglement (of the NOON type) that may be considered to be embedded in the separable state. We conclude that it is the existence of entanglement (of the NOON type) in the state of light used, not details of entanglement such as the degree of entanglement and relative weight of entanglement in the state, that determines the degree of the resolution improvement in quantum lithography. The visibility of the pattern and the total deposition rate, however, depend on the details of entanglement.