We report a scalable linear optical scheme for generating entangled states of multiple ququarts in which the individual single-ququart state is prepared with the biphoton polarization state of frequency-nondegenerate spontaneous parametric down-conversion. The output state is calculated with the full consideration of the higher order effect (double-pair events) of spontaneous parametric down-conversion. Scalability to multiple-ququart entanglement is demonstrated with examples: linear optical entanglement of three and four individual biphoton ququarts.
@article{arxiv.0708.0447,
title = {Scalable scheme for entangling multiple ququarts using linear optical elements},
author = {So-Young Baek and Yoon-Ho Kim},
journal= {arXiv preprint arXiv:0708.0447},
year = {2007}
}