Precision Survey Institute develops phase-locked vortex matter-wave interferometer

Recently, the research team of Jiang Kaijun, Institute of Precision Measurement Science and Technology Innovation, Chinese Academy of Sciences developed a vortex matter wave interferometer based on ultracold atomic gas, and observed the phase locking phenomenon of interference fringes on the two spin components
.

Interference is a fundamental phenomenon in classical wave mechanics and quantum mechanics, and interferometers based on it can accurately measure physical quantities by measuring the phase shift between different paths or channels
.
The ultracold atomic gas has the characteristics of pure composition, good coherence, and precisely controllable internal and external states.
In recent years, the matter-wave interferometer based on this system has become an important tool for precise measurement and fundamental physics research
.
At present, the matter wave interference realized in the ultracold atomic gas is mainly realized by manipulating the translational degrees of freedom of the matter wave to achieve beam splitting, and observing the matter wave interference fringes with different linear momentums for phase measurement
.
On the other hand, the rotation represented by angular momentum is another important degree of freedom of the system, and the angular momentum in the ultracold quantum gas is closely related to quantum phenomena such as vortex and superfluid of the system
.
A new type of vortex matter-wave interference can be realized based on different angular momentum states in ultracold atomic gas, which is expected to be used to measure the physical quantities such as the external magnetic field, rotation, inter-particle interaction and geometric phase of the system
.
The premise of realizing vortex matter-wave interference is the controllable preparation and manipulation of vortex states in ultracold atomic gas
.
In recent years, the progress in the study of the interaction between Laguerre-Gaussian light carrying angular momentum and cold atoms has laid the foundation for the establishment of a vortex matter-wave interferometer
.

In recent years, the research team has carried out research on the regulation of the vortex optical field of ultracold atomic gas, and mastered the preparation, manipulation and measurement of ultracold atomic vortex state by using the vortex optical field to drive two-photon Raman transition, and measured the spin- Quantum phase transitions of angular momentum coupled ultracold atomic gases [Physical Review Letters 122, 110402 (2019)]
.

Based on the previous work, the research team used a bias magnetic field to generate a large second-order Zeeman frequency shift between the three magneton energy levels of the F=1 hyperfine energy level of the rubidium 87 atom
.
Using a pair of Raman beams with different angular momentums to induce two-photon transitions, they obtained the first beam splitter of an interferometer whose arms have different spin and angular momentum (vortex states); using radio frequency pulses As the second beam splitter, the interference of the vortex matter wave is achieved on both spin states (corresponding to the two output ports of the beam splitter)
.
By choosing the right amount of detuning for the Raman light and the RF pulse, ensuring that the atoms are populated only at two magneton energy levels, a lossless beam splitter is created
.
Different from linear interference fringes produced by linear momentum interference, angular interference fringes were observed experimentally
.
Through the analysis of the interference pattern, it is found that the dry fringes on the two spin states have an inverse phase relationship (π phase difference), which is not affected by the angular momentum difference of the two vortex states, the composition of Raman light, and the ultracoldness.
Effects of experimental parameters such as atomic free expansion time
.
The researchers proposed a scheme to measure the magnetic field using a vortex matter wave interferometer, and evaluated the sensitivity of the magnetic field measurement, pointing out that the scheme can measure the magnetic field of limited size, and the measurement sensitivity is not affected by the fluctuation of the atomic number
.
This work provides an experimental basis for constructing novel quantum sensors based on vortex matter-wave interference
.

The related research results were published in npj Quantum Information under the title of Phase-locking matter-wave interferometer of vortex states
.
The research work was funded by the Key R&D Program of the Ministry of Science and Technology, the National Natural Science Foundation of China, the International Team of the Chinese Academy of Sciences, and the Hubei Provincial Innovation Group Project
.

Experimental Configuration of Vortex Matter Wave Interferometer

EXPERIMENTAL MEASUREMENT OF THE PHASE RELATIONSHIP BETWEEN TWO SPIN STATES IN INTERFERENCE FRINGES