Groundbreaking 8-Photon Qubit Chip Accelerates Quantum Computing

By National Research Council of Science & Technology November 16, 2024

Collected at: https://scitechdaily.com/groundbreaking-8-photon-qubit-chip-accelerates-quantum-computing/

South Korean researchers have developed a groundbreaking photonic quantum circuit chip that promises to accelerate the global race in quantum computation.

This chip, capable of controlling up to eight photons, marks a significant leap forward in manipulating complex quantum phenomena like multipartite entanglement.

Breakthrough in Photonic Quantum Circuit Development

A team of South Korean researchers has achieved a major milestone by developing an integrated quantum circuit chip that uses photons, or light particles. This breakthrough is expected to boost their position in global quantum computation research.

The Electronics and Telecommunications Research Institute (ETRI) announced the creation of a photonic integrated-circuit chip capable of controlling eight photons. This innovative system allows researchers to investigate complex quantum phenomena, including multipartite entanglement, which arises from interactions among the photons.

Achieving Quantum Entanglement Milestones

Through extensive research into silicon-photonic quantum circuits, ETRI has successfully demonstrated 2-qubit and 4-qubit quantum entanglement, achieving record performance for a 4-qubit silicon photonics chip. These accomplishments were the result of collaboration with KAIST and the University of Trento in Italy, and the findings have been published in the highly regarded journals Photonics Research and APL Photonics.

As a further advancement, ETRI recently demonstrated 6-qubit entanglement using a chip designed to control 8-photonic qubits. The 6-qubit entanglement represents a record-breaking achievement in quantum states based on a silicon-photonic chip.

Promising Future for Photonic Quantum Computers

Quantum circuits based on photonic qubits are among the most promising technologies currently under active research for building a universal quantum computer. Several photonic qubits can be integrated into a tiny silicon chip as small as a fingernail, and a large number of these tiny chips can be connected via optical fibers to form a vast network of qubits, enabling the realization of a universal quantum computer. Photonic quantum computers offer advantages in terms of scalability through optical networking, room-temperature operation, and the low energy consumption.

A photonic qubit can be encoded using a pair of propagation paths of a photon, with one path assigned as 0 and the other as 1. For a 4-qubit circuit, 8 propagation paths are required, and for 8 qubits, 16 paths are needed. Quantum states can be manipulated on a photonic chip, which includes photon sources, optical filters, and linear-optic switches, and are finally measured using highly sensitive single-photon detectors.

The 8-qubit chip includes 8 photonic sources and approximately 40 optical switches that control the propagation paths of the photons. About half of these 40 switches are specifically used as linear-optic quantum gates. The setup provides the fundamental framework for a quantum computer by measuring the final quantum states using single-photon detectors.

The research team measured the Hong-Ou-Mandel effect, a fascinating quantum phenomenon in which two different photons entering from different directions can interfere and travel together along the same path. In another notable quantum experiment, they demonstrated a 4-qubit entangled state on a 4-qubit integrated circuit (5mm x 5mm). Recently, they have expanded their research to 8 photon experiments using an 8-qubit integrated circuit (10mm x 5mm). The researchers plan to fabricate 16-qubit chips within this year, followed by scaling up to 32-qubits as part of their ongoing research toward quantum computation.

Quantum Hardware Developments and Goals

Yoon Chun-Ju, Assistant Vice President of the Quantum Research Division of ETRI, said, “We plan to advance our quantum hardware technology for a cloud-based quantum computing service. Our main goal is to develop a lab-scale system to strengthen our research capabilities in quantum computation.”

Lee Jong-Moo with ETRI’s Quantum Computing Research Section, who led this achievement, stated, “Research for the practical implementation of quantum computers is highly active worldwide. However, extensive long-term research is still needed to realize practical quantum computation, especially to overcome computational errors caused by noise in the quantum processes.”

Reference: “Quantum states generation and manipulation in a programmable silicon-photonic four-qubit system with high-fidelity and purity” by Jong-Moo Lee, Jiho Park, Jeongho Bang, Young-Ik Sohn, Alessio Baldazzi, Matteo Sanna, Stefano Azzini and Lorenzo Pavesi, 16 July 2024, APL Photonics.
DOI: 10.1063/5.0207714

The silicon photonics quantum chip research has been conducted as part of ETRI’s in-house New Concept Research Project, “Exploration of Silicon Photonics-Based Quantum Computer,” and is supported by the National Research Foundation of Korea as part of their Quantum Computing Development Project.