Quantum Interferometric Optical Lithography: Exploiting Entanglement to Beat the Diffraction Limit

Classical optical lithography is diffraction limited to writing features of a size $\lambda /2\mathrm{}$ or greater, where $\lambda$ is the optical wavelength. Using nonclassical photon-number states, entangled $N$ at a time, we show that it is possible to write features of minimum size $\lambda /\left(2N\right)$ in an $N$-photon absorbing substrate. This result allows one to write a factor of $N^2$ more elements on a semiconductor chip. A factor of $N=2\mathrm{}$ can be achieved easily with entangled photon pairs generated from optical parametric down-conversion. It is shown how to write arbitrary 2D patterns by using this method.