Einstein's equivalence principle predicts that a preponderance of virtual electron-positron pairs over virtual photons inside the quantum vacuum at shorter scales (e.g. dark matter galactic halo) will gravitationally attract from the positive zero point quantum pressure that is three times stronger than the anti-gravitation negative energy density causing a 3D isotropic spherical halo spatial curved geometry. Reference pp 25-26 "Cosmological Physics" John Peacock, Cambridge Press.
"In summary, the vacuum polarization alters the Josephson frequency-voltage relation in the presence of a strong magnetic field and results in a weak dependence of the Josephson constant on the magnetic field strength. This remarkable manifestation of a fine nonlinear quantum field effect in a collective phenomenon in condensed matter could be observed in a dedicated experiment, that would literally be a measurement of the vacuum polarization with a voltmeter."
We argue that the vacuum polarization by the virtual electron-positron pairs can be measured by studying a Josephson junction in a strong magnetic field. The vacuum polarization results in a weak dependence of the Josephson constant on the magnetic field strength which is within the reach of the existing experimental techniques.