In optical field at present, there is a rapidly developing field, known as Structured light. As the name implies, it make people see the smaller, more compact, more focused image of a wide field of vision, less photon detectionby by changing the structure of "patterns" of light, such as the amplitude and phase and polarization, cutting, cutting and etc. Light can be packaged as a new high bandwidth communication. Like a tailor, by cutting plain fabrics into different patterns and types.
Structured light is increasingly being used in technology. For example, policemen use structured light to photograph fingerprints in 3D scenes. Whereas previously they used tape to extract fingerprints, now they can use a camera and digitally squish fingerprints, which allows the identification process to begin before the officer leaves the scene. The following image shows a structured light pattern designed for surface inspection and an arc welding robot equipped with a camera and a structured laser light source that enables the robot to automatically track welds (below).
Structured light is increasingly being used in technology. For example, policemen use structured light to photograph fingerprints in 3D scenes. Whereas previously they used tape to extract fingerprints, now they can use a camera and digitally squish fingerprints, which allows the identification process to begin before the officer leaves the scene. The following image shows a structured light pattern designed for surface inspection (top right) and an arc welding robot equipped with a camera and a structured laser light source that enables the robot to automatically track welds (bottom left).
The question is, how to create and control the state of this light and how far can it be pushed to its limit? The mainstream tool for constructing the light of this state comes from lasers, but because the complexity of the required dedicated laser is challenged, customized geometries and/or elements are usually required. Only two-dimensional paradigms of pattern and polarization are used, that means access to two-dimensional classical entangled light, mimicking qubits of 1 and 0.
Now, scientists in China and South Africa, recently published a paper in the journal Nature-Light. They reported that they simply and directly create arbitrary dimensional quantum class classical light from lasers. For the first time, very simple lasers available in most university teaching laboratories are used to display eight-dimensional classical entangled light. Then, the research team continued to manipulate and control this quantum-like light, thus creating the first classical entangled greenberg-horn-zerlinger (GHZ) state, a well-known set of high-dimensional quantum states.
As shown in the figure, a simple laser consisting of only two standard mirrors is used to produce high-dimensional classical entangled light, which reflects a state of the art, which is different from the popular example of two-dimensional Bell state.
Professor Forbes, director of this research project, said :" it is worth noting that not only can we create such a strange state of light, but their light sources are as simple as you can imagine, just a few criteria needed ." That is, people realize that the key "extra" degrees of freedom require only a new mathematical framework to identify them. This method allows the formation of any quantum state by simply labeling the wave-like rays generated by the laser and then controlling them from the outside with a spatial light modulator. In a sense, the laser produces the desired size, while subsequent modulation and control mold the results into some desired state. To prove this, the researchers produced all the GHZ states that span an eight-dimensional space.
No one has ever created this high-dimensional classical entangled light in the past, so researchers need to invent a new measurement method to transform the tomography technology of high-dimensional quantum states into a language and technology, which are suitable for their classical light analogues. The result is a new tomography of classical entangled light, revealing its quantum-like correlation beyond the standard two-dimensional.
This work provides a powerful way to create and control high-dimensional classical light with quantum-like properties, paves the way for exciting applications in quantum metrology, quantum error correction, and optical communication, and provides many more versatile bright classical light for fundamental research to excite quantum mechanics.
