The LANL laboratory in the United States uses quantum light emitters to generate single photon light sources

Recently, the Los Alamos National Laboratory (LANL) in the United States has developed a method for quantum light emitters, which stacks two different atomic thin materials together to achieve a light source that generates circularly polarized single photon streams. These light sources can also be used for various quantum information and communication applications.

According to Han Htoon, a researcher at Los Alamos, this work shows that single-layer semiconductors can emit circularly polarized light without the need for an external magnetic field.

Previously, this effect could only be achieved through the high magnetic field generated by bulky superconducting magnets, coupling quantum emitters to very complex nanoscale photonic structures, or injecting spin polarized charge carriers into quantum emitters. Our proximity effect method has the advantages of low manufacturing cost and high reliability.

Polarization is a means of encoding photons, therefore this achievement is an important step in the direction of quantum cryptography or quantum communication. With a light source that generates a single photon stream and introduces polarization, we basically merge the two devices into one.

The research team stacked a single molecule thick layer of tungsten selenide semiconductor onto a thicker layer of nickel phosphorus trisulfide magnetic semiconductor. Using atomic force microscopy, the research team created a series of nanoscale indentations on thin layer materials.

When the laser is focused on the material pile, the 400 nanometer diameter indentation generated by the atomic microscope tool has two effects. Firstly, the indentation forms a "well" or "depression" in the potential energy landscape. The electrons of the tungsten selenide monolayer fall into the depression. This stimulates the emission of a single photon from the well.

Nanoindentation also disrupts the typical magnetic properties of the underlying nickel phosphorus trisulfide crystal, generating local magnetic moments pointing outward from the material. This magnetic moment circularly polarizes the emitted photons. In order to experimentally confirm this mechanism, the team first collaborated with the pulse field facility of the Los Alamos National High Magnetic Field Laboratory to conduct high magnetic field spectroscopy experiments. Then, the team collaborated with the University of Basel in Switzerland to measure the tiny magnetic field of the local magnetic moment.

The team is currently exploring methods to adjust the degree of circular polarization of single photons through electronic or microwave stimulation. This capability will provide a method for encoding quantum information into photon streams. Further coupling between photon flow and waveguide will provide photon circuits, allowing photons to propagate in one direction. This circuit will become a fundamental component of the ultra secure quantum internet.

Source: OFweek