Quantum-enhanced rubidium atomic magnetometer based on Faraday rotation via 795 nm stokes operator squeezed light

With the help of Stokes operator (S) over cap (2) squeezed state (also called polarization squeezed state (PSS)) of 795 nm light, rubidium-87 (Rb-87) atomic magnetometer based on Faraday rotation (FR) has been implemented and characterized. The PSS of Stokes operator (S) over cap (2) of 795 nm light has been prepared by means of coherently combining the polarization coherent state (PCS) of a linearly p-polarized bright 795 nm light beam and a linearly s-polarized squeezed vacuum state (SVS) generated by a 397.5 nm ultraviolet laser pumped sub-threshold optical parametric oscillator (OPO) with a PPKTP bulk crystal inside the OPO cavity. PSS with a squeezing level of -3.7 +/- 0.3 dB has been achieved around the analysis frequency of 10 kHz. At different transitions of D-1 line, various frequency detuning, and reasonable atomic vapor cell's temperature, FR has been measured and compared. To decrease absorption (scattering) losses and the back-action from atomic spin noise to the probe beam's polarization noise for maintaining the quantum properties of PSS of Stokes operator (S) over cap (2) of 795 nm light, we had to run our magnetometer with Rb-87 vapor cell's temperature below 60 degrees C, at which the PSS was almost destroyed. The sensitivities of magnetic field measurement were characterized via measuring signal-to-noise ratio of the alternating current calibrated magnetic field signal with a balanced polarimeter. Under the conditions of the atomic number density of similar to 5.8 x 10(10) cm(-3) (T similar to 40 degrees C) and the probe beam with a detuning of similar to-400 MHz relative to the 5S(1/2) (F (g) = 2) - 5P(1/2) (F (e) = 1) transition of Rb-87 D-1 line, a typical sensitivity of similar to 19.5 pT (Hz(1/2))(-1) has been achieved employing PSS of Stokes operator (S) over cap (2) as the probe, compared with a sensitivity of similar to 28.3pT (Hz(1/2))(-1) using PCS as the probe. We preliminarily demonstrated that the quantum-enhanced sensitivity in a Faraday-rotation-based Rb-87 atomic magnetometer with the help of PSS of 795 nm light.

Automated summary

The study successfully implemented and characterized a rubidium-87 atomic magnetometer based on Faraday rotation using polarization squeezed state (PSS) of 795 nm light. By adjusting different parameters in the experiment, the sensitivity of magnetic field measurement was effectively optimized.