Despite the great success of the standard model (SM), there still exist mysteries like the nature of dark matter, the strong $CP$ problems, etc. To solve them, many theories proposed new bosons beyond the SM that can mediate new forces. Here, we report the latest results of searching for possible new long-range spin-spin-velocity-dependent forces (SSVDFs), based on specially designed iron-shielded ${\mathrm{SmCo}}_5$ spin sources and a spin exchange relaxation free comagnetometer. With help from the similarity analysis method, new constraints on some forms of SSVDFs between electrons have been obtained, which represent up to more than 11 orders of magnitude tighter limits than previous experiments for the force range of 5 cm–1 km.

In a hybrid pumping alkali-metal vapor cell filled with both K and Rb atoms, the K atom spins are optically pumped by the laser and the Rb atom spins are polarized by the K spins through spin exchange. We discovered that the ac Stark shift of the Rb atom spins, caused by the far-off-resonant pumping laser tuned to the K absorption lines, was mixed together with the ac Stark shift of the K atom spins through fast spin exchange. This mixing is studied and we demonstrate a K-Rb-${}^{21}\mathrm{Ne}$ comagnetometer in which the ac Stark shift of the Rb atom spins is eliminated by compensating for the Rb ac Stark shift with the K ac Stark shift. An ac Stark shift elimination method has been developed.

Atomic co-magnetometers can be utilized for high-precision angular velocity sensing or fundamental physics tests. The sensitivity of a co-magnetometer determines the angle random walk of an angular velocity sensor and the detection limit for a fundamental physics test. A high-sensitivity K-Rb-²¹Ne co-magnetometer, which is utilized for angular velocity sensing, is presented in this paper. A new type of spin relaxation of Rb atom spins, which can broaden the zero-field magnetic resonance lines of the co-magnetometer, is discovered. Further studies show that the spin relaxation of Rb atoms is caused by a high Rb electron magnetization field. With this discovery, the total relaxation rate of Rb atoms is optimized to improve the sensitivity of the co-magnetometer. Moreover, its sensitivity is optimized by suppressing various noises. Especially, to suppress laser-related noises, the co-magnetometer is designed such that the sensitive axis of the co-magnetometer can be fixed to the direction in which the projection input of the earth’s rotation is 0. This is called a rotating co-magnetometer. A magnetic field sensitivity of 1.0 fT/Hz^−1/2@5 Hz, which is equal to an angular velocity sensitivity of 2.1 × 10⁻⁸ rad s⁻¹ Hz^−1/2@5 Hz, is demonstrated using a spherical vapour cell with a diameter of 14 mm.

The chip-scale hybrid optical pumping spin-exchange relaxation-free (SERF) atomic magnetometer with a single-beam arrangement has prominent applications in biomagnetic measurements because of its outstanding features, including ultrahigh sensitivity, an enhanced signal-to-noise ratio, homogeneous spin polarization and a much simpler optical configuration than other devices. In this work, a miniaturized single-beam hybrid optical pumping SERF atomic magnetometer based on a microfabricated atomic vapor cell is demonstrated. Although the optically thin Cs atoms are spin-polarized, the dense Rb atoms determine the experimental results. The enhanced signal strength and narrowed resonance linewidth are experimentally proven, which shows the superiority of the proposed magnetometer scheme. By using a differential detection scheme, we effectively suppress optical noise with an approximate five-fold improvement. Moreover, the cell temperature markedly affects the performance of the magnetometer. We systematically investigate the effects of temperature on the magnetometer parameters. The theoretical basis for these effects is explained in detail. The developed miniaturized magnetometer has an optimal magnetic sensitivity of 20 fT/Hz^1/2. The presented work provides a foundation for the chip-scale integration of ultrahighly sensitive quantum magnetometers that can be used for forward-looking magnetocardiography (MCG) and magnetoencephalography (MEG) applications.

In a K-Rb- ²¹ Ne co-magnetometer, the Rb electron magnetic field which is experienced by the nuclear spin is about 100 times larger than that of the K in a K- ³ He co-magnetometer. The large electron magnetic field which is neglected in the K- ³ He co-magnetometer coupled Bloch equations model is considered here in the K-Rb- ²¹ Ne co-magnetometer to study the low frequency magnetic field suppression effect. Theoretical analysis and experimental results shows that in the K-Rb- ²¹ Ne spin co-magnetometer, not only the nuclear spin but also the large electron spin magnetic field compensate the external magnetic field noise. By comparison, only the ³ He nuclear spins mainly compensate the external magnetic field noise in a K- ³ He co-magnetometer. With this study, in addition to just increasing the magnetic field of the nuclear spins, we can suppress the magnetic field noise by increasing the density of the electron spin. We also studied how the magnetic field suppression effect relates to the scale factor of the K-Rb- ²¹ Ne co-magnetometer and we compared the scale factor with that of the K- ³ He co-magnetometer. Lastly, we show the sensitivity of our co-magnetometer. The magnetic field noise, the air density fluctuation noise and pumping power optimization are studied to improve the sensitivity of the co-magnetometer.

We describe a single beam compact spin exchange relaxation free (SERF) magnetometer whose configuration is simple and compatible with the silicon-glass bonding micro-machining method. Due to the small size of the vapor cell utilized in a miniature atomic magnetometer, the wall relaxation could not be neglected. In this study we show that Ne buffer gas is more efficient than that of the other typically utilized gas species such as nitrogen and helium for wall relaxation reduction theoretically and experimentally. 3 Amagats (1 Amagat=2.69×10¹⁹/cm³) Ne gas is filled in the vapor cell and this is the first demonstration of a Cs-Ne SERF magnetometer. In order to reduce the laser amplitude noise and the large background detection offset, which is reported to be the main noise source of a single beam absorption SERF magnetometer, we developed a laser power differential method and a factor of approximately two improvement of the power noise suppression has been demonstrated. In order to reduce the power consumption of the magnetometer, the Cs based atomic magnetometer is studied. We did an optimization of the magnetometer and a sensitivity of 23fT/Hz^1/2@100Hz has been achieved. This is the first demonstration of a single beam Cs based SERF magnetometer.