Recently, the team of Academician Guo Guangcan of China University of Science and Technology cooperated with Professor Lu Zhengtian, and made new progress in the chip-based cold atom magneto-optical trap system, and realized the cold atom magneto-optical trap system based on dual chips for the first time. This achievement is helpful to realize quantum precision measurement, quantum simulation and calculation related applications, such as quantum gravimeter, quantum memory and so on.

magneto-optical trap can cool and capture atomic vapor, which has a wide application prospect in the field of modern atomic physics. The cold atom ensemble obtained by magneto-optical trap is the necessary basis for realizing long-coherence time quantum bits and realizing applications such as quantum precision measurement, quantum simulation and calculation based on it.

however, the traditional magneto-optical trap system is partially restricted in its further scalable application, such as multi-channel free-space beam alignment, huge anti-Helmholtz coil, and strict coincidence of magnetic field and light field center. Therefore, how to realize miniaturization and even chip-based magneto-optical trap system has attracted extensive international interest. Among them, the magneto-optical trap based on grating chip greatly simplifies the incident system of six beams of space light in the traditional magneto-optical trap, which is not only small in size, light in weight, rich in optical windows and high in scalability, but also has great potential in mobile quantum precision measurement systems and integrated quantum computing systems.

But for another important part of magneto-optical trap-magnetic field coil, it can only be realized by three-dimensional coil. If the size of the magnetic field coil is large, thicker wires and stronger current are needed to realize the required magnetic field gradient, resulting in large power consumption and serious heating. If the size of the coil is reduced, the coil may seriously obstruct the optical path and reduce the available optical window size.

For this reason, Zou Changling, a team of academicians from Guo Guangcan, and Professor Lu Zhengtian cooperated to propose a brand-new planar magnetic field coil configuration, which only needs a 3cm 3cm chip to generate the quadrupole magnetic field required by magneto-optical traps. Based on the micro-nano machining center of the University of Science and Technology of China, they independently designed and processed the magnetic field chip and grating chip which matched each other, and based on this, they successfully captured more than 16 low-temperature 87Rb atoms, which proved the practicability of this novel configuration. They combined the independently designed magnetic field chip and grating chip to realize the cold atom magneto-optical trap system based on dual chips. Related results were recently published online in the journal Physical Review Applied.

The two chips designed by the aforementioned team are small in size, light in weight and low in power consumption, which frees up more optical windows. In addition, it is also very convenient to use. Two chips can be stacked together, and only transparent glue is needed to be fixed outside the vacuum glass window, and cold atoms can be captured by the incidence of a single laser beam. Among them, the magnetic field chip of 6.4W (Watt) can be driven, and it is expected to use portable storage battery to supply power, which will promote the further integration of small magneto-optical trap system.

The team further explored the relationship between the performance of magneto-optical trap and various parameters under the new configuration. In the experiment, the researchers observed that with the increase of magnetic field current, the detuning of local optimal light field will increase approximately linearly. Based on the energy level configuration of atoms, the team suggested that this may be caused by the reduction of magnetic field size, and the experiment confirmed the new characteristics of this magneto-optical trap regulation, which is easily overlooked in the traditional three-dimensional large coil configuration. This research not only observed this important physical phenomenon in experiments, but also provided a new understanding of the performance of magneto-optical traps.

The reviewer commented on this: "I think this work will attract the attention of the atomic, molecular and optical (AMO) fields, where the grating magneto-optical trap (MOT) and micro MOT technology are becoming people's interests, and this work has a real impact and is closely related to practical applications."

Chen Liang, a graduate student in the Key Laboratory of Quantum Information, Chinese Academy of Sciences, is the first author of the paper, and Professor Zou Changling is the corresponding author of the paper. The above-mentioned research work was supported by the national key research and development projects, the National Natural Science Foundation, the special funds for basic scientific research business expenses of central universities and the open project of the State Key Laboratory of Market Supervision (time frequency and gravity measurement benchmark). Related achievements have been patented and authorized.

Proofreading: Ding Xiao