Ultra-sensitive Single-beam Atom-optical Magnetometer using Weak Measurement Method

Ultra-sensitive measurement of the magneto-optical rotation, due to interaction of linearly-polarized light passing through room-temperature Rb 85 atoms, in response to change in longitudinal magnetic field (\delta B_z ) is demonstrated using the weak measurement method. The polarization rotation angle measurement sensitivity (\delta \psi ) of 16 \mu~rad and hence of the magnetometer of 1 nT, achieved using the weak measurement method is better than the balanced optical polarimetry results by a factor of three. The improvement in the measurement sensitivity is realized via optical amplification of the polarization rotation angle via spin-orbit coupled light beam-field. The method is devoid of external rf modulation, allows for optimal tunability of sensitivity depending on the dynamic range of the applied magnetic field and the sensitivity can be further enhanced by operating in the Spin Exchange Relaxation Free regime of alkali spin polarization.