Scientists create an optical conveyor belt to move light-matter particles

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Researchers from RIKEN and NTT Research have developed a groundbreaking technique to control polaritons, which are particles that blend light and matter.

This innovative method uses the interference between two lasers to create what they call an “optical conveyor belt.”

This technology has the potential to revolutionize devices in quantum metrology and quantum information.

Published in the journal Nature Photonics, the study demonstrates how scientists used two lasers to form a dynamic landscape of energy, resembling moving valleys and hills.

This dynamic energy landscape influences a special state of polaritons known as a polariton condensate, which behaves like a laser.

The team introduced the optical conveyor belt to manipulate the energy landscape, allowing precise control over the interactions between polaritons. By adjusting the frequency difference between the lasers, they could move the conveyor belt at speeds approaching 0.1% of the speed of light, pushing the polaritons into a new state.

A key feature of this technology is non-reciprocity, where the behavior of the system differs depending on the direction of movement. This is essential for creating a topological phase of matter, a concept from mathematics where objects are classified based on their number of holes. In quantum materials, this concept translates into unique properties like movement without energy loss and other exotic behaviors.

Creating non-reciprocity in optical platforms is extremely challenging, but this simple and scalable experiment offers new possibilities for quantum technologies. The research team, led by Senior Research Scientist Michael Fraser, included contributors from Germany, Singapore, and Australia.

Fraser explained, “We created a topological state of light in a semiconductor structure by rapidly changing the energy landscape, introducing a synthetic dimension.” A synthetic dimension maps time into a space-like dimension, allowing the system to evolve in more dimensions and better achieve topological matter.

This work builds on a previous technique where lasers were used to rotate polariton condensates rapidly. By using the interference between two lasers, scientists could organize polaritons into energy bands, similar to how electrons are arranged in a material.

By controlling the dimensions, depth, and speed of the optical lattice, they achieved precise control over the band structure.

The polaritons experienced different potential energy landscapes depending on their direction, similar to the Doppler shift in sound. This asymmetry breaks time-reversal symmetry, leading to non-reciprocity and the formation of a topological band structure.

Photonic states with topological properties can significantly enhance optical devices, circuits, and networks by reducing noise and energy loss. The simplicity and robustness of this technique pave the way for topological photonic devices with applications in quantum metrology and quantum information, Fraser concluded.

Source: RIKEN.