Vacuum fluctuation
= Vacuum fluctuation
= Zero-point field
{synonym}
A <vacuum fluctuation> is a nonzero quantum variance in a <vacuum state>. For a single electromagnetic <normal mode>, dimensionless <optical quadratures> $a+a^\dagger$ and $-i(a-a^\dagger)$ have zero means and unit <variances> in the <vacuum state>, despite zero <photon number>. The mode's <zero-point energy> is $\hbar\omega/2$.