  The experimentally measured spectral density of current noise in Josephson
junctions provides direct evidence for the existence of zero-point
fluctuations. Assuming that the total vacuum energy associated with these
fluctuations cannot exceed the presently measured dark energy of the universe,
we predict an upper cutoff frequency of nu_c=(1.69 +- 0.05) x 10^12 Hz for the
measured frequency spectrum of zero-point fluctuations in the Josephson
junction. The largest frequencies that have been reached in the experiments are
of the same order of magnitude as nu_c and provide a lower bound on the dark
energy density of the universe. It is shown that suppressed zero-point
fluctuations above a given cutoff frequency can lead to 1/f noise. We propose
an experiment which may help to measure some of the properties of dark energy
in the lab.
