Center for Quantum Technology of the National Tsinghua University Developing Core Quantum Technologies in Taiwan

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Quantum technology is considered the key to the next generation of technology. The Center for Quantum Technology (CQT) in National Tsing Hua University has successfully utilized “photons” to complete the first outdoor quantum encryption communication test in Taiwan and established the first local quantum communication network based on the test.

Chung-Yu Mou, the director of CQT and professor of the Department of Physics, was interviewed by the MOST Center for Global Affairs and Science Engagement, during which he openly discussed novel subjects of quantum technology as well as outstanding research achievements of the members in CQT.

Application of Quantum Technology 

To develop core technologies for the second quantum revolution, CQT was established by National Tsinghua University in 2018. The purpose of the center is to conduct fundamental quantum research and develop local quantum technologies, particularly key technologies that can realize quantum computers and quantum communication. In addition, CQT aims to cultivate first-tier research young talents.

CQT focuses on four research topics, namely the construction of quantum computers, quantum communication, quantum measurement and simulation, and quantum materials. The ultimate goal of the center is to produce multiple superconducting qubits, establish quantum communication networks and test platforms for quantum key distributions, and realize continuous-variable quantum information as well as Majorana-Fermion-based topological qubits. 

Professor Mou said that during the early 20th century, the first quantum revolution promoted the invention of transistors, integrated circuits, and lasers based on the basic principles of quantum mechanisms, which laid down the foundation for the vigorous development of semiconductor and optoelectronic industries. Since 2015, quantum technology has arrived at a tipping point, where the number and decoherence time of qubits, the unit of quantum computers, have greatly increased. During this period, leading technology companies, such as IBM and Google in the United States, have made major breakthroughs in the research and development of quantum computers, thereby proclaiming the arrival of the “quantum technology era.”   

Successful Development of Quantum Encryption

Consisting of 50 members, CQT is one of the most complete and powerful quantum technology research teams in Taiwan. With the joint support of MOST and the Ministry of Education, Chih-Sung Chuu, a member of the center and associate professor of the Department of Physics, successfully completed the first local quantum encryption communication test in 2019, demonstrating Taiwan’s ability to independently develop key encryption technologies.

The research team utilized “photons,” the smallest component of light, to deliver the password required for encryption within the optical fiber network between campuses of National Tsing Hua University and National Chiao Tung University that were 3.44 km apart. In the quantum world, these extremely tiny particles exhibit many counter-intuitive properties, among which the most important features are the superposition of states and the entanglement. These bizarre features make the particles behave as if they have the ability to perform“cloning.”  This “quantum cloning” improves the computing power of quantum computers and optimizes the security of quantum encryption communication.

Professor Mou explained that, unlike general encryption algorithms, quantum encryption does not rely on complicated and difficult mathematical computations, but rather utilizes the characteristics of quantum states for encryption. Therefore, it is impossible to crack the encryption irrespective of the computing power. A successful development of quantum encryption can greatly improve data security when applied to the transmission of financial and military information.

In addition, the center’s research teams publish approximately 60 papers each year, among which about 7 to 8 papers are published in high-impact journals, marking the outstanding achievements of the center in international academic publications. In 2021, Professor Hao-Wu Lin of the Department of Materials of National Tsing Hua University supervised doctoral students in a project in collaboration with Chih-Sung Chuu, associate professor of the Department of Physics, as well as Northwestern University of the United States. During the project, they developed highly stable, self-repairing perovskite quantum dots as a single-photon light source based on the self-developed spray synthesis method. This achievement was not only selected as the cover story by the international journal of ACS Nano but also triggered heated discussions in the research community. The brightness of a single photon produced by the quantum dots broke the world record by reaching 9,000,000 photons per second, making it a breakthrough in quantum communication and quantum computing applications.
 

Promotion and Prospect of Domestic Quantum Technology 

Existing prototype quantum computers that were developed internationally can provide at most 50-100 qubits. Recently, IBM announced the latest 127-qubit quantum processor, Eagle, allowing quantum computers to cross the 100-qubit barrier.

Despite promising prospects, quantum technology faces multiple challenges in the actual implementation. Professor Mou indicated that quantum computers are required to have at least 1000 reliable, error-free qubits for commercialization. However, under the existing quality of qubits, this requires at least 1 million qubits to implement error correction. The quantum state is fragile, it cannot be duplicated, and it has a short survival. Meanwhile, flying qubits (photons) will decay and are difficult to scale up in read-out measurement. Therefore, the real application of quantum computers is still far off.

Nevertheless, the research teams at the National Tsing Hua University are still committed to the development of quantum technology with local characteristics and the invention of qubits with both high quality and long survival. Superconducting qubits are the basis of quantum computers manufactured by major international companies. Professor Mou’s team already has the capability to manufacture 4 to 5 qubits with the decoherence time reaching international standards (about 70 to 80 microseconds). Further development can turn the qubit chip into one with multiple bits of more than 50, thereby allowing it to surpass the computing or simulation capabilities of conventional computers, thus possessing industrial application potentials.

Recently, MOST has joined forces with the Ministry of Economic Affairs and the Academia Sinica to form a national quantum research team to develop independent technologies for quantum software and hardware, and build the first national quantum technology research base. With the establishment of the prototype and the commitment of substantial research resources, Professor Mou was optimistic that Taiwan would definitely master key quantum technologies and realize industrialization under continuous development.

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