A method for quantum spin amplification includes spin-polarizing an ensemble of quantum spins in an initial spin state to generate a transversely-polarized sensing spin state. The quantum spins identically have an upper energy state and a lower energy state. The sensing spin state accumulates a phase shift that transforms the sensing spin state into a phase-accumulated spin state having first and second transverse polarization components. The phase-accumulated spin state is transformed into an intermediate spin state by rotating the first transverse polarization component into a longitudinal polarization component of the intermediate spin state. The ensemble is then coupled to an auxiliary mode, during which the intermediate spin state evolves such that the second transverse polarization component is amplified into an amplified transverse polarization. This amplified transverse polarization is then measured.