A research team led by Professor Ra Young-sik of the Korea Advanced Institute of Science and Technology (KAIST) has successfully implemented a three-dimensional cluster quantum entanglement state, which is key to quantum error correction technology. This marks a breakthrough in one of the challenges for the commercialization of quantum computing.
Measurement-based quantum computing is a form of quantum computing that implements quantum operations by measuring a cluster state with a special quantum entanglement structure. Quantum entanglement refers to a state where two particles have a consolidation that is not visible to each other. When there is an entangled state, measuring the state of one particle leads to the other particle having the same state. This quantum entanglement structure can be utilized for communication or computation.
Measurement-based quantum computing is centered on creating cluster quantum entanglement states, but until now, a two-dimensional structured cluster state has been used. However, to reach a level suitable for commercialization, it is necessary to implement a much more complex three-dimensional structured cluster state. Previous research had limitations in creating a two-dimensional cluster state.
The KAIST research team developed technology to control femtosecond time-frequency modes to implement quantum entanglement. Using this, they succeeded in generating a three-dimensional structured cluster quantum entanglement state for the first time in the world.
A femtosecond laser is a device that emits strong light pulses for an extremely short duration. The research team irradiated a femtosecond laser onto a nonlinear crystal to simultaneously generate quantum light sources across various frequency modes, utilizing this to create a three-dimensional structured cluster quantum entanglement.
Professor Ra Young-sik noted, "This research marks the first successful case of producing a three-dimensional cluster quantum entanglement state, which was difficult to implement with existing technologies," adding, "It will serve as an important stepping stone for future measurement-based quantum computing and fault-tolerant quantum computing research."
References
Nature Photonics (2025), DOI: https://doi.org/10.1038/s41566-025-01631-2