This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: A research group in Japan has demonstrated a world-record 10-channel multiplexed quantum photonic interface based on an integrated waveguide array, a key technology for optically interconnecting multiple quantum computers. The study is published in the journal Optica.
Neutral-atom quantum computers are expected to use arrays of approximately 10,000 atoms, with each atom serving as a qubit. However, fault-tolerant universal quantum computers are expected to require more than one million qubits for error correction. One promising route to this scale is to interconnect multiple quantum processors by distributing entangled photons between them.
This requires a multiplexed quantum photonic interface capable of linking many qubits in parallel. Previous multiplexing approaches mainly relied on parallel optical fibers and were limited to only a few channels. Their insufficient integration density and wide atom spacing also made them difficult to apply to conventional neutral-atom quantum computers.
In this study, the research group led by Professor Takashi Yamamoto, deputy director of the Center for Quantum Information and Quantum Biology at the Graduate School of Engineering Science, the University of Osaka, in collaboration with the National Institute of Information and Communications Technology (NICT) and Hamamatsu Photonics K.K., developed an optical system incorporating an integrated optical waveguide array and demonstrated parallel photon delivery and detection from a neutral-atom array. Photons emitted from 10 atoms spaced at micrometer-scale intervals were coupled into 10 parallel channels of a 32-channel waveguide array, transmitted through optical fibers and detected in parallel. The experiment also confirmed negligible interchannel crosstalk and correlations between the quantum states of the atoms and the polarization states of the emitted photons, supporting the interface's potential for multiplexed atom-photon entanglement and quantum-processor networking.
The approach is expected to be scalable to approximately 100 parallel channels. Photon detection was performed using a multichannel superconducting nanostrip photon detector system based on technology developed by Shigehito Miki, director of the Superconductive ICT Device Laboratory at the Kobe Frontier Research Center, Advanced ICT Research Institute, NICT. The system was newly developed as a research system for this experiment by Hideki Shimoi, manager at the Electron Tube Division of Hamamatsu Photonics K.K.
"Through research and development spanning from neutral-atom arrays to superconducting nanostrip photon detector systems, we have achieved the first demonstration of a multiplexed optical interface," Professor Yamamoto said. "Going forward, we will scale up the degree of multiplexing and work toward connecting neutral-atom quantum computers, accelerating progress toward a fault-tolerant networked quantum computer." This research represents an important step toward networked quantum computers with the scalability needed for fault-tolerant universal quantum computing. By enabling multiple quantum processors to be interconnected through parallel photonic links, the technology could support large-scale quantum computing architectures similar to modern data centers, where many computing modules work together as a single system.
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