The ultracold atomic interferometric gyroscope developed in this project is designed to meet the demands of fully autonomous navigation for modern strategic weapons, aiming to provide angular velocity measurement equipment with higher sensitivity and improved stability. Compared to optical gyroscopes, atomic gyroscopes exhibit superior theoretical angular velocity resolution due to their matter-wave properties. To fully leverage these theoretical advantages, it is essential to maximize the utilization of atomic matter-wave characteristics. Ultracold atoms, with their extremely low kinetic energy distribution and high coherence, are ideal for high-precision measurements and are regarded as the most promising medium for unlocking the potential of atomic interferometers. However, due to technical challenges in preparing and manipulating ultracold atoms, gyroscopes in this field are still in their infancy. Although existing ultracold atomic gyroscopes generally lack high angular velocity resolution, they hold significant future potential.
This system combines atomic Sagnac interferometry with magnetic levitation technology based on a quadrupole magnetic trap, achieving a gyroscope sensitivity surpassing 3×10⁻⁵ rad/s. Innovatively integrating ultracold atoms, Bragg lattice pulses, and quadrupole magnetic trap orbital guidance, this project has developed a compact, high-precision gyroscope with breakthroughs in angular velocity accuracy, system mobility, and matter-wave interference mechanisms. Additionally, benefiting from the low noise of the static magnetic trap, this instrument achieves internationally leading angular velocity sensitivity per unit area.
Figure 1. Ultracold Atomic Interferometric Gyroscope System
Based on the Bose-Einstein condensate (BEC) prepared and loaded into the magnetic trap in prior steps, we first apply a Bragg pulse to split the atomic cloud and propel it into the orbit. When the atoms reach the farthest point from the trap center, a second Bragg pulse—orthogonal to the first—is applied, imparting momentum to the atoms for circular motion around the center of the quadrupole magnetic trap. After completing an integer number of orbits, the atomic cloud returns to its pre-split position, where a third Bragg pulse is applied to partially restore the atoms to the zero-momentum state. The proportion of atoms in this state contains the phase information required for measurement. During the experiment, both upper and lower atomic clouds undergo interference measurements, and differential processing eliminates common-mode noise. Leveraging the Sagnac effect, the phase difference is extracted from the results to calculate the angular velocity. After several hours of measurement, the system achieves an angular velocity resolution exceeding 3×10⁻⁵ rad/s.
Figure 2. Schematic Diagram of Atomic Interference
Since the system employs a quadrupole magnetic trap to confine atoms for interferometric measurements, only Rb⁸⁷ atoms in the specific magnetic sublevel (mF = -1) can be trapped. Thus, maximizing the preparation of Rb⁸⁷ atoms in the -1 state is critical. To achieve this, a quadrupole magnetic field and a bias magnetic field are activated during optical trap evaporation cooling. By adjusting parameters such as magnetic field duration, gradient strength, and central position, the distribution of atoms across magnetic sublevels in the resulting BEC can be controlled. Experimentally, the proportion of -1 state atoms was increased from 1/3 to over 97%, with theoretical analysis and modeling conducted to support the process. The figure below shows the distribution of atoms across magnetic sublevels in the BEC under three different parameter sets during magnetic state selection. As illustrated in Figure 3c, the optimized process successfully concentrates most atoms in the -1 state.
Figure 3. Alteration of Atomic Magnetic Moments via Magnetic State Selection