A team of scientists from HSE University, the RAS Institute of Spectroscopy, and Moscow Institute of Physics and Technology have developed a cold atom chip for devices with high accuracy of measurements. The researchers are currently working to create atomic clocks which could be used on spacecraft and the ISS. The paper has been published in Optics & Laser Technology.
Cold atom chips are devices capable of trapping and holding atoms cooled to ultralow temperatures. As early as in the late 1970s, scientists at the Institute of Spectroscopy demonstrated that atomic gases could be effectively cooled by laser radiation and conducted the world's first experiment of this kind. Subsequently, an approach was developed for using atom chips to generate and control ultracold atomic ensembles. Until recently, however, no working atom chips were available in Russia. A team of scientists from the RAS Institute of Spectroscopy, HSE and MIPT have presented a new solution: the first Russian chip for cooling and trapping atoms.
The chip consists of a silicon wafer with microwires. An electric current flowing through the wires generates a magnetic field around the chip with the minimum magnitude in a certain point. Atoms tend to migrate to a low-field location which is energetically favourable for them. This is how magnetic traps work, allowing scientists to control and use the trapped atoms.
An atom's temperature is linked to its kinetic energy—the energy of motion. To reduce an atom's velocity, one needs to take away its energy and thus cool it down. This can be achieved by certain configuration of laser fields around the chip. This approach allowed the researchers to cool rubidium atoms down to a temperature of about 200 µK, making them unable to escape the magnetic traps.
To prevent the microchip wires from exploding due to overheating caused by the electric current, the wires were made of silver and gold with a thickness of several micrometres, making them capable of accommodating a stronger current of up to 10 amperes.
Cold atoms are used in applications which require high accuracy, for example, in GPS navigation systems. We are now working to design atomic clocks to be installed on satellites. The principle of their operation is that a frequency generator must continuously maintain a reference frequency equal to that of rubidium’s microwave atomic transition. By studying the atomic excitation spectra, we can see how the electromagnetic radiation interacts with atoms. The lower the atomic temperature, the narrower the spectral lines and the more accurately they can be measured. In our case, the more accurate the clock will be.
Atom chips can be used not only as a source of cold atoms, but also as a sophisticated device in its own right. The researchers suggest using atom chips to measure gravitational waves.
There are projects under consideration to use atom chip-based systems on the board of satellites. Atoms could be used to detect the passage of gravitational waves through a satellite constellation. By looking at interference patterns, it could be possible to study not only gravitational waves but also the interaction with dark energy. The international community expects to implement this project in the mid-2030s.
Text author: Ekaterina Korchagina