Experimental Test of Gravitationally Induced Quantum Interference

We call attention to a feasible laboratory experiment with an outcome that depends necessarily on both Planck's constant and the gravitational constant. A neutron interferometer for which the two beams enclose an area of ~ 6 ${\mathrm{cm}}^{2}$ can be cut from a single crystal of silicon. A shift of ~ 10 fringes is anticipated when the interferometer is rotated 180\ifmmode^\circ\else\textdegree\fi{} about an axis parallel to both the earth's surface and the incident neutron beam.