The Electronics and Telecommunications Research Institute (ETRI) has succeeded in developing the world's first 8-photon qubit integrated circuit chip using light particles, or photons.

ETRI announced on the 4th that it has completed a system that can control eight photons by expanding the silicon photonics quantum chip and is currently experimenting with quantum phenomena caused by eight photons.

By applying photonic technology, it has become possible to implement quantum entanglement in space and time.

The research team has been steadily pursuing research on silicon photonics quantum chips.

Last year, the research team, in collaboration with KAIST and the University of Trento in Italy, demonstrated world-leading performance by implementing two-qubit and four-qubit quantum entanglement on a four-qubit silicon photonics chip that can control four photons.

These results were published in the world-renowned academic journals ‘Photonics Research’ and ‘APL Photonics’ respectively.

After publishing papers on 2-qubit and 4-qubit quantum entanglement, ETRI produced a chip expanded to 8-qubits and confirmed the 6-qubit quantum entanglement phenomenon this time.

The research team developed this 8-qubit generation and control quantum chip to achieve 6-qubit quantum entanglement. He said that the results of the phenomenon verification are very significant as it is the world's first achievement based on silicon-based photonic technology (Si Photonics) integrated circuits.

In particular, the path that a photon takes is divided into two, and if it goes up it is expressed as 0 and if it goes down it is expressed as 1. For 4 qubits, the path that light takes is 8 in total, including up and down, and for 8 qubits, it is 16.

The researchers created a state in which qubits are strongly quantum entangled with each other within the chip.

The photonics-based technology that the researchers have achieved is one of the most promising ways to create a quantum computer.

This is a technology that creates a silicon photonics quantum chip that includes a photon-based quantum circuit on a silicon chip the size of a fingernail, and connects multiple quantum chips into a network to implement universal quantum computing.

In particular, photon-based quantum computers have the advantages of high speed, room-temperature operation, low error rate, scalability, and low energy consumption.

Manipulate and measure quantum information encoded in optical systems using quantum light sources, linear optical devices, and single-photon meters.

ETRI created a new chip by incorporating various optical components, such as photon generators, phase modulators, and switches, into it to control the path of light and achieve quantum interference.

This makes it possible for computers to perform their basic roles of information transmission and conversion.

The chip contains eight nonlinear photon pair generation sources and about 40 optical switches that control the light path, and about 20 of the optical switches act as quantum gates.

This provides the basic framework for a quantum computer that measures quantum states using single-photon detectors.

The researchers discovered an interesting quantum phenomenon called the Hong-Ou-Mandel phenomenon, in which two photons coming from different directions meet and influence each other, causing them to move together. The effects were measured on-chip.

The research team created a 5 mm × 5 mm 4-qubit integrated circuit and, following the HOM interference experiment, published a paper describing quantum phenomena that occur when the paths of four photons become entangled, including two more photons.

Currently, we are creating an 8-qubit integrated circuit measuring 10 mm x 5 mm and studying quantum phenomena occurring from a total of 8 photons.

The research team plans to further improve the perfection of the technology in the future, challenge the development of a 16-qubit chip this year, and then expand development to 32 qubits and use it for quantum computing application research, including quantum machine learning (ML).

ETRI's Yun Cheon-ju, head of the Quantum Technology Research Center, said, "We are planning to improve technological perfection in the future and provide cloud services within five years using quantum computers, like foreign cases. We plan to make the system work even on a laboratory scale and move forward with pioneering new areas of academic research."

Dr. Jong-Moo Lee of the ETRI Quantum Computing Lab, who led this achievement, said, “Research for the practical implementation of quantum computers is being conducted competitively around the world. Much research is still needed to implement and commercialize quantum computing that overcomes computational errors caused by qubit noise.”

ETRI's silicon photonics quantum chip research was developed with the support of ETRI's own new concept research project (nicknamed Seedling Project), "Silicon Photonics-based Quantum Computer Exploration Research" and the National Research Foundation of Korea's Quantum Computing Development Project.