The smallest spot in optical lithography and microscopy is generally limited by diffraction. Quantum lithography, which utilizes interference between groups of N entangled photons, was recently proposed to beat the diffraction limit by a factor N. Here we propose a simple method to obtain N photons interference with classical pulses that excite a narrow multiphoton transition, thus shifting the "quantum weight" from the electromagnetic field to the lithographic material. We show how a practical complete lithographic scheme can be developed and demonstrate the underlying principles experimentally by two-photon interference in atomic Rubidium, to obtain focal spots that beat the diffraction limit by a factor of 2.
@article{arxiv.quant-ph/0411163,
title = {Quantum lithography by coherent control of classical light pulses},
author = {Avi Pe'er and Barak Dayan and Marija Vucelja and Yaron Silberberg and Asher A. Friesem},
journal= {arXiv preprint arXiv:quant-ph/0411163},
year = {2011}
}