  A simple tabletop setup based on a superconducting quantum interference
device is proposed for testing the gravitational interaction. A D-shaped
superconducting loop has the straight segment immersed inside a massive sphere
while the half-circle segment is wrapped around the sphere. The superconducting
condensate within the straight arm of the loop thus bathes inside a
gravitational simple harmonic oscillator potential while the condensate in the
half-circle arm bathes in the constant gravitational potential around the
sphere. The resulting phase difference at the Josephson junctions on both sides
of the straight arm induces a sinusoidal electric current that has a frequency
determined by the precise gravitational potential due to the massive sphere.
