Parametric up conversion of the vacuum
arXiv:quant-ph/9803054
Abstract
The theory of parametric down conversion of the vacuum, based on a real zeropoint, or "vacuum" electromagnetic field, has been treated in earlier articles. The same theory predicts a hitherto unsuspected phenomenon - parametric up conversion of the vacuum. This article describes how the phenomenon may be demonstrated experimentally.
See also http://www.keyinnov.demon.co.uk and http://xxx.lanl.gov/abs/quant-ph/9712050