Japan’s RIKEN and NTT scientists create ‘optical conveyor belt’ for quasi particles…

23 May 2024

…and Coherent launches novel fiber for lidar and cold atom trapping for quantum computing.

Using interference between two lasers, a research group led by scientists from RIKEN and NTT Research, both based in Japan, have created what they call an “optical conveyor belt” that can move polaritons — a type of light-matter hybrid particle — in semiconductor-based microcavities.

They conclude that this achievement could lead to the development of new devices with applications in areas such as quantum metrology and quantum information. The work is described in Nature Photonics.

The scientists used the interference between two lasers to create a dynamic potential energy landscape for a coherent, laser-like state of polaritons known as a polariton condensate.

They achieved this by introducing a new optical tool – an optical conveyor belt – to enable the control of the energy landscape and the interactions between neighboring particles. By further tuning the frequency difference between the two lasers, the conveyor belt moves at speeds of the order of 0.1 percent of the speed of light, driving the polaritons into a new state.

Non-reciprocity—a phenomenon where system dynamics are different in opposing directions—is a crucial ingredient for creating what is known as an artificial topological phase of matter. Quantum materials can also be engineered with a non-zero topology, which in this case is more abstractly embedded into the band structure.

Opportunities for quantum technologies

The RIKEN/NTT announcement states that, “it is extremely challenging to introduce non-reciprocity into engineered optical platforms, and this simple, extendible experimental demonstration opens new opportunities for emerging quantum technologies incorporate functional topology.”

The research group, including first author Yago del Valle Inclan Redondo, and led by Senior Research Scientist Michael Fraser, both from RIKEN CEMS and NTT Research, together with collaborators from Germany, Singapore and Australia, have conducted a study in this direction.

Fraser commented, “We have created a topological state of light in a semiconductor structure by a mechanism involving rapid modulation of the energy landscape, resulting in the introduction of a synthetic dimension.”

A synthetic dimension is a method of mapping a non-spatial dimension, in this case time, into a space-like dimension, such that the system dynamics can evolve in a higher number of dimensions and become better suited to realizing topological matter.

Using this simple experimental scheme involving the interference between two lasers, the scientists were able to organize polaritons in precisely the right dimensions to create an artificial band structure, meaning that the particles organized into energy bands like electrons in a material.

“Photonic states with topological properties can be used in advanced opto-electronic devices where topology might greatly improve the performance of optical devices, circuits, and networks, such as by reducing noise and lasing threshold powers, and dissipationless optical waveguiding. The simplicity and robustness of our technique opens new opportunities for the development of topological photonic devices with applications in quantum metrology and quantum information,” said Fraser.

New fiber for lidar and cold atom trapping for quantum apps

Optical networking and laser company Coherent, has launched a novel single-mode, polarization-maintaining erbium-ytterbium optical fiber for high-power 1550 nm, narrow linewidth, and single-frequency amplifiers. The company states that it is “now the first company to support pure SM, PM optical fibers for >20 W average power capabilities.”

Coherent adds that its innovation is “merging exceptional high-power performance and superior beam quality to achieve unique performance characteristics previously unavailable”. Additionally, the fiber features a 130 µm geometry made possible by a proprietary manufacturing technology.

“This is the world’s first exclusively single-mode, polarization-maintaining erbium-ytterbium co-doped fiber for high-power applications,” said Kanishka Tankala, VP Specialty Fiber Products. “It is optimal for quantum computing and coherent lidar research while also significantly improving the power scalability of current single-frequency amplifier systems.”