Gravity Probe Spin: Prospects for Measuring General-Relativistic Precession of Intrinsic Spin Using a Ferromagnetic Gyroscope

An experimental test at the intersection of quantum physics and generalrelativity is proposed: measurement of relativistic frame dragging and geodeticprecession using intrinsic spin of electrons. The behavior of intrinsic spin inspacetime dragged and warped by a massive rotating body is an experimentallyopen question, hence the results of such a measurement could have importanttheoretical consequences. Such a measurement is possible by using mm-scaleferromagnetic gyroscopes in orbit around the Earth. Under conditions where therotational angular momentum of a ferromagnet is sufficiently small, aferromagnet's angular momentum is dominated by atomic electron spins and ispredicted to exhibit macroscopic gyroscopic behavior. If such a ferromagneticgyroscope is sufficiently isolated from the environment, rapid averaging ofquantum uncertainty via the spin-lattice interaction enables readout of theferromagnetic gyroscope dynamics with sufficient sensitivity to measure boththe Lense-Thirring (frame dragging) and de Sitter (geodetic precession) effectsdue to the Earth.