More Than One Word From Quantum Dots To Quantum Rings

More Than One Word From Quantum Dots To Quantum Rings

Jan 25, 2018

Quantum computation has become one of the hottest research projects nowadays. As a carrier of information, the implementation of qubits is a key technology in quantum computer research.


Recently, the cooperative R & D team from the Chinese Academy of Sciences Institute of microelectronics and tide electronic information industry limited company, joint Chongqing University of Posts and Telecommunications, Xiamen University researchers published papers, put forward to construct electronic semiconductor quantum ring quantum computer theory to enrich the qubit implementation.

As the author, the Chinese Academy of Sciences Institute of microelectronics integrated circuit lead technology R & D center researcher Wu Zhenhua told Technology Daily reporter, said: "with the construction of a semiconductor quantum ring quantum bit, which is a new idea of the existing mature semiconductor technology to build a quantum computer based on."

The size of the transistor is close to the physical limit

In the last 40 years, the microelectronics industry has been following Moore's law for continuous and rapid development.

"But with the progress of technology, the integration of devices is getting higher and higher, the number of transistors on the chip is increasing, and the size of single transistor is getting smaller and smaller. It can be said that the development of the current semiconductor chip is approaching the physical limit of size. The era of Moore's law is coming to an end. It is urgent to develop new computing principles and new device architectures to meet the growing demand for computing. Wu Zhenhua explained, "in this context, the scientists all over the world to study the laws of quantum mechanics, quantum computing and information technology development, in order to develop practical quantum computer instead of traditional computer, super ultra high quantum parallel computing ability."

"Quantum computers achieve the growth of computing power by superposing and entangling quantum phenomena. Quantum superposition enables the qubits to have both the values of 0 and 1 at the same time, and can be 'synchronized'. With each additional qubit, the operational performance is doubled. " Another paper communications author, Dr. Liu Yu, a wave of artificial intelligence and high performance computing, said.

At present, Google, Microsoft, IBM, Intel and other technology companies have already laid out the research of quantum computing. Liu Yu said, IBM claimed to have successfully developed a 50 qubit quantum hardware prototype; Google chief John Martinez Google has 22 qubit chips revealed in October last year; Chinese also in early May 2017 released the world's first quantum computer beyond early classical computer successfully. The 10 qubit entanglement, is expected in the near future can be manipulated to achieve 20 superconducting qubits.

To meet a number of specific "indicators" to better quality

Quantum bit quality implementations generally need to meet several specific requirements, such as the physical carrier of easy implementation, easy preparation and initial operation, long coherence time etc..

At present, the realization schemes of quantum bits mainly include superconducting circuits, trapped ions, semiconductor quantum dots, diamond vacancies, topological arbitrary subgroups, photons and so on. Each technology has its own advantages and disadvantages. The future route is not yet clear. Wu Zhenhua told reporters. According to his introduction, the semiconductor quantum dot solution has the most core advantage in the above scheme. It can develop and operate on the basis of the existing semiconductor technology, and is easy to implement high density integration.

But the strong quantum confinement effect in semiconductor quantum dots makes the electron coherent time short and the electronic entanglement difficult. To solve this problem, we use the configuration interaction (configuration interaction) method, from a theoretical study of the electronic states including 3 to 6 electrons in the semiconductor quantum ring, found the number of electrons in quantum ring, electronic coupling entanglement between different, and with the external magnetic field, electric field and different show the different characteristics, so as to realize the control of quantum states. In addition, our research also systematically expounds the scheme of measuring the characteristics of quantum rings by optical measurement. " Liu Yu said.

Can be realized by using current semiconductor technology

  In the view of Wu Zhenhua and Liu Yu, the construction of quantum bits with multi electron semiconductor quantum rings is a new idea for the existing single electron semiconductor quantum dots scheme. The main obstacle to realize quantum computing is that the quantum state used for computing is difficult to maintain, which is often said to have a short coherent time. The research shows that compared with semiconductor quantum dots, the limiting potential of semiconductor quantum rings is easy to adjust, and the electron coherence time is longer, which helps to achieve more qubits operation. The semiconductor quantum dots can manipulate the single electron spin, which is very difficult for the experiment. The multi electron quantum ring uses the number of electrons and the spin state of the electron to realize the qubits, so it has more operable degrees of freedom. In addition, electrons are bound in the zero dimensional space in the quantum dots. The electrons in a quantum ring also have the degree of freedom in a quasi one dimensional orbital motion, which provides a new coding possibility outside the charge of the spin.

Moreover, like semiconductor quantum dots, the quantum ring can also be realized by using the existing semiconductor technology, so that it can smoothly transition from classical semiconductor chip to quantum chip based on the existing technology. Wu Zhenhua said.

This new research result is the fruitful result of the cooperation between industry and research. Liu Yu said: "the research used a more rigorous and precise theoretical simulation method, but the amount of computation is huge. The cooperation between the Microelectronics Institute and the wave group's industry university research cooperation has brought into full play the advantages of wave in the high-performance computing area. The two sides will continue to promote cooperation and seek new breakthroughs in the field of quantum computing. "