Two-photon interferometric quantum photon lithography for light of wavelength λ is capable of beating the Rayleigh diffraction limit of resolution λ/4 to the level of λ/8. The required twin single-photon states $|1{〉}_a|1{〉}_b,$ which are converted into maximally entangled states by a 50:50 beam splitter, can be generated from a nondegenerate parametric amplifier initially in vacuum states and with a weak pump field. Increasing the pump strength can slightly increase the production rate of the desired state and it will also increase the production of the twin two-photon states $|2{〉}_a|2{〉}_b,$ which leads to an unwanted background term. In this paper we show that, assuming a weak pair coherent state as input to the amplifier, quantum interference can be used to quench the production of the $|2{〉}_a|2{〉}_b$ state and to enhance the production of the $|1{〉}_a|1{〉}_b$ state by almost sixfold.

• Received 14 November 2002

DOI:https://doi.org/10.1103/PhysRevA.67.043801